Well, I own an older
Scamp, not a
Casita, and I have only had it for 10 months, but did a lot or research. I wouldn't be speaking up, but the OP posted over a day ago, and only has one reply, so thought I would chime in about what I kinda know.
Casitas along with Scamps should have their snap caps replaced every few years as they deteriorate with UV from the sun. Extremely simple process if they are done regularly and the washer under the rivet remains intact, quite a bit more involved if you must replace the washer - then the entire rivet must be replaced. This is not a terrible job, but it is much easier to just replace the caps regularly.
You must regularly check for any window/vent/door/etc
leaks. If you find some, it is often best to remove the offending item and re-install it using new butyl tape and or seals as required. Once properly installed, these items seldom leak for many more years. My
Scamp is 17 years old and I have detected no
leaks due to seal failure. That said, I did have the door seal replaced earlier this month as a preventative - the original seal was starting to crumble.
The next big area of concern, regarding
leaks is your plumbing. Must be checked regularly since most of it is hidden away inside cabinets. Repair any leaks as soon as they are discovered. I had to replace both the hand pump which was leaking, and the drain trap from which the nipple that the drain connects to had broken off. Both of these were very cheap, simple fixes.
Every six months or year, check your floor for any signs of water damage. Make sure to check under the trailer and inside all cabinets and benches - the hidden areas. This is easier to do in a
Scamp than a Casita, since the floor is exposed. The Casita encapsulates the wood inside of
fiberglass. This makes the Casita floor somewhat more protected initially, but still vulnerable through screw holes, plumbing holes, etc. Some have found the damage to be so hidden that it was hard to detect. No floor is easy to replace, but often the Scamp can just have the bad portion cut out and replaced. When a Casita floor goes bad, it is often the entire wood structure inside the
fiberglass that is mush and it is quite difficult to replace. At least that is my understanding.
Other maintenance items to be acutely aware of are the age/condition of the
tires - age is of greatest concern. and the condition and lubrication of the wheel bearings. Pretty simple to check and correct if a problem is found.
Brakes, as on any vehicle, should also be checked periodically.
Regarding the appliances - most are standard RV appliances which tend to last quite a long time, but as with all things, they will occasionally fail. As far as I know, all the appliances on my 17 year old Scamp are original and they are still functioning as expected.
Hopefully some others with more personal and more in depth knowledge will chime in and offer some more advice.