I've had Win2K Pro since late 2000, it dual boots with XP Pro SP3. I still use the OS on occasion, like when outdoors or when traveling. I realize that all Microsoft support ends in August, 2010. This was my first OS, and although Windows 7 Pro is my main OS (I skipped Vista), it has sort of a sentimental value to me, I first discovered the internet through it. After next year, what can I expect to happen? I know that some are still running 95 & 98.
It will continue to run, just as it always has. There will be no updates to speak of, although it's possible that Microsoft might release updates for glaring security problems. New hardware won't be supported, nor will many new software packages. As you say, 95, 98, and earlier versions of Windows and DOS still run and still have thier uses.
I'll keep mines! The best I've ever had (didn't try 7 though).
What did happen quickly with W95 (as MS wanted to push W98) and slowly with Nt4 (since professional users have long-lasting memory) is that updates may disappear from MS' site some day. It did in 2009 for Nt4 which appeared in 1996 and was maintained up to 2006. So download and backup everything you need for a complete fresh install.
O yes, I forgot to tell: automatic updates may stop some day.
What will also happen sooner is that you'll find less software that runs on it. Not a worry for document editing, acceptable for games, but watch out security software! You can keep an old firewall (download+backup hence) but you need fresh signature updates for the antivirus. Though, Avast plans to stop W95 support at the end of this month, 2009/12.
For a non-connected use: no limit! I'm happy to have several W95 on older hardware.