So for example my Temple High Guard has been Stranglevined for two rounds and I have paid the Upkeep. The Stranglevine at the point is up 4 Life. Now Deathlock comes out in round 3. During the Upkeep phase, I pay the Upkeep for the 3rd Crush token. However with Finite Life out on all Living Creatures/Conjurations the Stranglevine does not gain any more Life. However during the next round I kill the Deathlock and then during the next Upkeep phase, I pay Stranglevine's Upkeep. Does Stranglevine now have 6 or 8 additional Life?
[mwcard=DNJ10]Stranglevine[/mwcard]
X = the number of crush tokens.
Strangle gain Life = 2X
The life gain is a trait that is always active. There is no window to apply the effect.
From Codex
Finite Life
(Object Trait)
This creature cannot heal, regenerate, or gain Life. If the creature gained Life before it gained this trait, it keeps that Life but cannot gain additional Life. All Nonliving objects have Finite Life.
So you get to keep all the life you have. [mwcard=MW1J19]Deathlock[/mwcard] does not revert the life gained from a revealed Rhino Hide.
Now, if a creature is under the effect of D'lock and then reveals a rhino hide, he does not get the life increase. If the D'lock is destroyed the next round he would then gain the life increase. Life gain as per the trait has no window to be active, it is either active or not. When the finite life is removed you life is equal to base life + any increases.
Back to s.vine. It has life = 2X. So in your example when the finite life is removed, it would get a "surge" of life since finite life is no longer preventing the gain.