My mistakes in the beginning were making due with an uncomfortable bed. I really tried to make the tri fold conversion van bench seat/bed comfortable, and even fooled myself into thinking so, and was the fool for it, sacrificing my lower back and sleep quality, and attitude.
It was a happy day when the bench seat was hacked into pieces small enough to go into a recycling bin, and a plywood platform and a quality firm foam rubber mattress replaced it.
Other mistakes in the beginning were regarding batteries. I was one of the many who assumed short drives were more than enough to recharge a battery, and that it did not really matter if the battery was fully charged regularly. My electrical loads were quite light at that time, and group 27 batteries were lucky to last beyond 8 months. I got well acquainted with the inverter's low voltage alarm, and dealing with trying to warranty batteries, which I killed, due to overwhelming ignorance of what they require to yield even a decent lifespan. I am ashamed that I warrantied so many batteries. I am not somebody who wants something for nothing, holding such an attitude in utmost contempt, but I was a battery murderer, and blamed the victim, and the seller for my own extreme foolishness/ ignorance, and arrogance.
Other regrets are not getting a 12v compressor fridge and enough solar to run it earlier. I think of all those times I had to throw away spoiled food, when I could not afford to, how many times I had to leave and pack up camp just to resupply for ice, how much money I wasted on block and chipped Ice itself, and time spent emptying stinky cooler water, destinkifying the cooler and its compartments, and the waste of so many ziplock baggies whose seals failed and contaminated the food within. Regarding the Solar, well there were so many times I couldn't listen to the radio or watch a DVD or even keep the light on for too long, as I did not want to have to waste fuel just to drive, just to recharge the batteries, which were so capacity compromised already they had little usable capacity left anyway.
Now with an extra insulated 12v Vitrifrigo front loading fridge, and 198 watts of solar, and an awesome vehicular battery charging system, I simply never worry about spoiled food, The fridge is always 33.5 to 35.5F, and I make my own ice, and from basically March21 to when the clocks fall back in autumn, I have a significant solar surplus and can basically use as much electricity as I want, within reason, and only have one single 90 AH capacity AGM battery, that so far, has lived longer than any other heavily cycled battery I have had, and all indications via the proper measuring tools and much experience and interest in the subject, are it retains much of its original capacity at 2.5 years and 250+ deep cycles to less than 60% and another 100+ shallower cycles to ~80% charged.
In '07 I gutted and rebuilt my interior for maximum storage under the new platform bed. This allowed me to be able to carry way too much weight, and as it was out of sight, it was out of mind, killing MPGS and wearing out the brakes and drivetrain faster carrying stuff I did not need, or even remember that I had with me.
Travelling light is less burdensome than carrying everything might conceivably need. It is far too easy to imagine a scenario where it would be great to have such and such a device/implement/accessory/tool with you. In most instances, not having it is not something worthy of more than a shoulder shrug. The time when a certain random possession one was loathe to leave behind/sell/give away, carried just for its specific purpose, saves the day, is quite rare.
There can be a million examples where this or that, carried, was well worth it and the speaker breaks their arm patting themselves on the back for having had it with them, but for every 1 thing that does save the day, 10 things carried along will never have the chance to.
So, beware of the 'just to have, just in case' items. They are good at making their way onto lists, and often serve no purpose.
Warm and fuzzies are hard to put a price tag on. It is really an individual thing, and only obvious in hindsight, whether it was a worthwhile useful warm and fuzzy, or a simple waste of space, time, effort and/or emotion.
Also, when I first started getting on automotive/RV forums, I really believed the replies were correct, not realizing most replies were just a kid in the back of the classroom with their arm raised going Oh OHH OHH! trying to impress themselves and others that they had a reply, while being overwhelmingly wrong and ignorant. Learn to ignore those who present their opinion as absolute fact, and their way is the only way, and anybody else doing it differently is a mouth breathing knuckle dragger.
The other regrets are having to rely on mechanics when something went wrong. In 2002 I spent 450$ to have a fuel injector replaced. An 80$ product that takes less than 5 minutes to replace. I just had no knowledge that it was the culprit, even though I had the skills and tools to easily replace it. Whatever vehicle you get, try and get the factory service manual( check Ebay motors) for that specific year, rather than a haynes or Chilton manual which is much less in depth as it can cover vehicle models spanning 20+ years.