Not happy with Forest River!

My APEX is by Coachmen, by Forest River. I have a 10 year warranty on the floor. check your manual as well

I don't know if you dealt with directly with the factory or went through your dealer. I do know that Cedar Creek has fixed problems after the warranty period has expired. It is sometimes a case of getting a hold of the right person to present your issue. My suggestion is to take pictures of the affected areas, inside and outside, and submit that with a detailed explanation of the issues. Don't get belligerent or demanding, just present the facts. At the moment I don't know the person for you to contact. But we are headed to the FROG rally tomorrow and I'll bet someone there can tell me.
It is too late for this year, but Forest River makes many repairs to their products each year at the FROG rally. And not all of the repairs they perform are the result of the manufacturing process. Some are operator error, but they will take care of you.
FWIW, we are on our fourth fifth wheel and the second Cedar Creek and we have never had the customer service on the other brands like this. We didn't have major problems, but FR still took care of us even out of warranty.

Not all manufacturers have only a one year warranty. Some including Jayco have 2 year warranties covering their RV's. Might be part of the reason why the Jayco Jay Flight line of trailers have been and are the highest volume selling trailers of all manufacturers constantly since 2005.

Nope, we don't own a Jayco RV and haven't since the early 1980's and it was excellent also but wouldn't mind buying a new Jayco Eagle RV as they are much better than most other brands and very well insulated. Our Carriage Carrilite 5th wheel trailer and our Lance TC simply refuse to wear out or have ever leaked at all and still look like new and have zero repairs done or needed. Like the OP, we sure wouldn't want a Forest River RV or Thor RV either as who wants the aggravation and financial woes of a cheaply built corner cut issues after a few years that is constantly being posted on the many forums?

Could be said a little nicer. Caulking and seals should be checked regularly, at least yearly. But yes, once the warranty expires it is all on the owner unless you can prove a manufacturing defect. Then you MIGHT get some relief. But a leak after only 3-4 yrs is, in my opinion, a sign of poor construction. Our SOB (some other brand) is 8 years old and never a leak of any kind.

Three to four years old. What do the seals look like? When is the last time you reseal ed things? What do you expect 1 year warranty after that it's on your dime with any manufacturer