In reply to Webster:
> for water Ice generally late march is the latest to expect good conditions, snow ice (such as the classic point 5 and zero gulies) are often at their best in april/may (I did my last winter route on 17th may last winter) and indeed there was routes in condition in june last year. as always with winter climbing it is a lottery but late season snow ice on ben nevis is the most reliable of winter mediums and even after prolonged thaws routes can come back into condition over night if its been a snowy winter.
Smiths Route is normally an ice fall and is typically in condition well in to April. Some other ice falls are also typically in condition really late in the season such as tower scoop. Ice can be particularly resistant to thaw under the right conditions.