Snooze Tabs got introduced in the Firefox to help the users focus their attention on whatever they were doing online, and to remove the causes of distractions for the time being and save those items for later. By Hitting the snooze icon one would be able to dismiss the tabs that are currently irrelevant, and then it sets an alarm to bring those sites or elements back when you want them.
As a Chrome user, I haven't tried this feature yet, but yes, this feature itself is quite interesting and undoubtedly useful for writers like us, as we work on different things simultaneously. In this way, the browser won't get overloaded.
There is no specific information on how many tabs you can snooze, but from the announcements in their official site, we can assume that the feature should be available for any number of tabs.
As it would work almost as closing the tab, or minimizing the tab, I don't think, there can be any restrictions for its usage, especially when the purpose of the feature is to close down unnecessary ones which would be automatically multiple in number.
But setting an Alarm for each of them seem to be quite difficult a task, as one needs to be highly organized and conscious to know his moods, his future timings. One should be able to predict his forthcoming situations, when those tabs would appear to be relevant again.