Spirit Strike will halve its bonus value upon each successive application when re-cast. For example, an originating +75 to the swing (suggested +25 to CS) will become a +113 bonus for the next strike. If re-cast a third time, the bonus will be +132 then +141, etc. (rounding up..). I might be off a digit or two but the general idea is that each cast of 117 will build on itself for the greater strike. I like the idea that each cast also raises the chances that you will be able to use it again, say 5% each. If it is reactivated though then it will be back to +75 (until re-casting).