“a lot” is pretty subjective.
Let’s say that before November, I don’t remember noticing any downtime with TiddlyHost.
Since November, there have been very noticeable downtime occurrences. I would not be surprised if some operating system and/or Web server software upgrade has caused some problems, and some eventual upgrade will fix things.
Pre-November, TiddlyHost was so stable that I find it pretty easy to believe it will be again whenever some upgrade/patch for whatever operating system and/or web server software is released. The normal reliability still outweighs the recent hiccups.
In the meantime, I download to a local drive any TW (on TiddlyHost) that I’ve significantly altered, so that I still have access to a recent TW instance when TiddlyHost is down.
Just like it is always important to have backups of local files, it is always a good idea to have backups of files on any web service.
BTW, I generally avoid modifying any copy of a TW instance I have on TiddlyHost. I don’t like figuring out the diffs between two TW instances when there’s an intertwingled mess of diffs.