You could get perhaps 2 seconds refunded for every unlaunched missile, with a minimum recharge time of roughly 15 seconds, even if you aborted after firing just a couple of missiles (So you can’t easily keep re-engaging it to bypass the 2 per target lock-on rule)
I generally find the tempest to be more of a burst weapon for very large or stationary targets, but the long cast time, fixed launch angle, and 2 per target limit on lock-ons tends to mean that 80% of the missiles go to waste.
With this setup, you can be a bit more economical with your launcher if you so choose, firing only enough to lock on to the given number of targets, or continuing to launch dumbfires for lucky hits or splash area denial.