Only just came across the question now, but I thought I would post an answer. That must be annoying. Firefox should not do that and does not do that for me or the vast majority of users. When Firefox updates you should not lose tabs that are set on your Homepage, or tabs that you have open. If as appears to be the case you are talking about the tabs set as homepages then thy are listed in an about:config preference and you may save that which makes it a few seconds of a job to reinstate them. The tabs will also be listed on the Troubleshooting information page (but not sure if that could truncate the listing if you have a lot.) I may not know what caused your problem and may not be able to solve it, but that may be a workround that saves you an hour.