PPF is personal decision. $3500 for an entire care (assuming its done right) is a good "deal" only as it relates to market pricing for PPF.
I personally have owned cars for many years/100k miles plus. And ended up 95% of the time selling them privately for the top of "private sale" price of KBB or higher. Those cars had no PPF.
I also wonder how easily PPF will come off after being on a car for many years, exposed to UV, etc. I hope it all comes off of all surfaces (especially plastic bumpers) without peeling off a single piece of paint with it..
As far as ceramic, whats your goal? I wash my cars by hand usually once a week (when weather is nice) and once a month I apply a spray on wax and hand buff for max gloss. Doing this keeps water beading small and tight and paint glossy. Once a year I'll break out the buffer and do a decontaminate process (spray on stuff) and then apply a one step cleaner wax. Easy, cheap, simple, effective. So no ceramic needed for me.