Based on the back version installation files I've kept on my HD for Calibre, I'm updating about every 6 months or so. Around that time a mobi from Amazon refuses to covert so it forces me to update. I appreciate the effort that goes into each update - my husband is a software writer so I know that it can take a lot to make changes - but I don't think I need to update every two weeks.
With the Kobo, unless I HAVE to update because of a huge bug or because I'm forced to do a factory reset, I don't do it. The version I have is working fine, I can read my books and make shelves to organize them, I have fonts that work. I have no issue with users who upgrade every time a new firmware version is released, it's just not what I do. If/when I have a big problem, I'll do it. Until then, as my husband has pointed out, if it's working why bother?