Hello;The heat of the water does not kill ick, it just speeds there life cycle allowing the salt to work.

I will add that the timeline is not set. The goal is to have water salt concentration at a high enough level so the salt will kill the parasite during the brief time right after it hatches from an egg. So for a while after the last parasite is visibly gone from the fish there can be unhatched eggs in the substrate. My take has been to continue treatment 7 to 10 days after the last visible parasite.
In at least one thread about ich the forum member turned out to not have dosed the water with enough salt. She explained that she loved her fish so much was why and was afraid of the suggested dose. Her approach made no sense in that a too low dose was pointless. The salt has to be at a concentration that will kill the parasite when it first hatches. Yes you can slowly sneak up on the salt dose but it does not start being effective until the killing concentration is reached (that is when the clock can start if you want to go for a strict ten days).
Good luck