Curious what the "end game" strategy is.

Seems like the strategy to 500 loops is, assuming you are running under gold boost:
Focus on maxing out Trouser Snake:
Freax10
Rapterx10 (but using 1 sec attack)
X10ing starting with Penguin for as many Super slots as you have.
x10ing starting with Asian Dragon for as many super slots as you have (Asian will hit 10 right around time raptor is no longer 1-shotting)


That'll get you up to 500 pretty much 1-shotting everything. (well, with each nymph 1 shotting non-bosses)

Not really sure where to go from there. Try for an "interim" girls or attempt to jump to girls that can take you up to 1k 1-shotting? I only had enough money at that point for 1 (and she'd need to be sexy-3 before it's possible), and about 1/2 the money needed for a second (also ~sexy 3, IIRC)

My gut reaction is switch to french charm & Robot (just to tide over a bit) then Chicken (sexy 3 1-shot to 1k) Demon (also sexy 3 1-shot to 1k), then Frog(sexy1), followed by squirrel(stage 3) etc.