I had to vote "once per day" because of the explicitly-given definition of "nova." My problem is, I don't care for that definition. I have a broader definition of what I consider to be "nova." That is, not that it necessarily is always your best tools 100% of the time, but that it is a very strong tool (such as a Daily power in 4e or 13A) which you can drop early in a fight to make a major difference right away. Though I would prefer to call it a "nova," for the purpose of argument I'll let the OP's definition stand and refer to my preference as a "mini-nova."
Understood by those lights, I think only low-level characters (e.g. before 5th level) should be limited to one "mini-nova" each day. Instead, I prefer that it be 2-3 "mini-novas" each day, spread out over 3-5 encounters each day. On a slow day where you're carefully shepherding your resources, you might be able to trounce all the fights you face. On a busy day, especially if you faced difficult opponents early on, you might be tapped for all your "big guns" before the halfway point.
If supplemented by encounter-like resources (personally, I find 5e's "two encounters per short rest" method tedious bookkeeping for little benefit, fully overshadowed by the negatives this approach induces), then this creates a reasonably interesting tension between hoarding and nova-ing at the strategic level, while reserving more context-specific choices for the tactical level. This can then be supplemented with robust rules at the strategic level for taking away (or allowing the expenditure of) daily or long-term resources for other benefits, completely outside tactical-level concerns.
With such a setup, there are interesting and worthwhile choices at all levels of play, and even though the two ends remain mostly distinct, each can influence the other in important ways. Screw up or fail to exploit your tactical resources, and you suffer a drain on strategic resources that can compound with time. Conversely, being profligate or miserly with your strategic resources, and you'll find the tactical layer becomes dramatically harder without any effort from the DM. This creates a ripe environment for actually learning to play better, which is one of the most important aspects of anything claiming to be a "game" and not just a puzzle.