I have a client that use CMS, Commerce and Find translated to 15 different languages. Now they want to expand and add 25 new languages, so a total of 40 languages. Most of the new 25 languages will just fallback to the existing english site. I spontaneously got the feeling that 40 languages could be quite heavy (bad for performance), but it's nothing but a gut feeling. To summarize, 15 translated sites and an extra 25 languages that fallback to english. In the future, the fallbacked languages might be translated as well.
One thing that made me a bit reluctant was not knowing whether the new languages, although fallbacked, would create extra documents in Find - and therefore risk reaching the document limit of our license.
Do you have any good or bad experiences with sites with many translated sites? If good - maybe shed some light on if you made some special adjustment to cope with the amount of languages. If bad - what is/was your issues, did you solve them and how did you solve them?