you may want to take a look at other threads like this: https://forum.inaturalist.org/t/how-confident-can-we-be-that-inaturalist-data-will-be-preserved/3248/13.
based on these questions, i suspect you might be contemplating a use for the system that is not really what it’s intended for. for example, i don’t think it’s intended to be a photo storage site, and i don’t think it should be used as the primary repository for critical data either.
personally, i’ve never lost any data that i’m aware of, but there definitely are infrequent bugs and reports of photos going missing, etc. if you are worried about losing information, you can always export the data, and of course, you should always keep your own copies of photos or other media that you would be sad about losing.
as far as i’m aware, the stuff that you input into the system will be there as long as you want it to be, and as long as iNaturalist continues to operate. you can help it continue to operate by occasionally providing a small cash gift (or a large one, if you are able), or by helping in other ways…