Keystone Canyon and the Valdez area ice climbs start to fade by late March and early April at best. The biggest issue is the rivers being frozen or not and that can be washed out by one small warm storm at any time. This winter has been snowy and semi cold so far compared to the nuclear meltdown winter we had last year.
If the weather is crap and raining in Valdez there are some more temperature resistant climbs north of Thompson Pass and reliable ice out in the Wrangells along the road to McCarthy.
Generally ice season runs from mid November towards the end of the 1st week of April. There will be some ice available after that but it can be spotty. Mid March can be prime for fat ice and big routes. Of course it is ice climbing and mother nature can change everything but I've climbed here for over 20 years and as a general rule of thumb those dates seem to work.