Your Internet activity may already be safely stored in one or more Internet archives. People are aware that all our scribblings may be of great interest to future historians and are making efforts to save it for them.
You may wish to make arrangements for your heirs to take over your sites. You could even set up a trust fund to pay for Internet hosting in perpetuity; that would not require very much funding at all, even a few hundred dollars is probably enough,
I'm 62, so, yes, I have thought about this. If the Internet had existed 200 years ago, I would love to read my ancestors postings. I was very unhappy when my grandmother, who had led a very colorful and adventurous life, tossed all her diaries because she felt no one would be interested. What a tragic loss!