This is one of those things I think could use some guidelines in the corebook, and probably in Edge (Or is it in Edge? I don't recall. And couldn't find anything on a brief skim through).
Mainly because the use of such talents are... very dependant on session length. A group that does 2 hour sessions gets a lot more use out of it than one doing a marathon 8 hour session. This actually makes those sorts of talents rather limited if you're (un?)fortunate enough to be in one of the latter cases. Sure there is a generally unspoken presumption in most of gaming that a session is about 4 hours, give or take, and it feels like most games are built around this presumption. But that's where the problem is. Any deviation from the average length either buffs or debuffs once per session. And especially in an 8 hour session, a once per session talent is almost worthless, a very limited resource indeed.
And yes, there is always working out with your GM - IF they are willing to, since ultimately they have the power to decide. So I'm rather firmly in the camp that issues like this should be in Black and White.