Also, rethinking this question:
My approach is "it must be beneficial to some extent" so I refresh early but do so conservatively so I'm not risking doing it more than is optimal, in this case probably too conservatively. If the Rip is Bloodtalons'd you're getting an additional 15% of Rip DPS for ~28 seconds, so on paper it would be okay to waste up to 28 * 15% = 4.2 seconds. If the Rip is not Bloodtalons'd then you would tend to refresh it closer to its 7.2 second mark so the benefit is a bit less. Clipping at <11s is probably fine in practice.
Sim'd it for fun, DPS gain was 11 and the DPS error is 42. So yeah, not significant at all but it doesn't seem to be a lost at least.