no slp's as far as im concerned.
if we tell you to do 300kts then i would expect you to until told otherwise.
there may be occasions when the controller has forgotten or it wasnt given in a handover so you would have to query it.
you are right that if suddenly you came back to minimum clean to enter a hold when i was expecting you to still be going a bit faster then you could compromise separation but i wouldn't expect a decent controller to be giving you crazy speeds when holding is occuring anyway.
this is similar to clearances where the current clearance negates the previous one regardless of levels that may occur in a STAR.