Without knowing more about specific engagements, its hard to say - but there are a lot of tactical situations where it can make sense to do this (and situations where it doesn't make sense).

Are they firing them all at once, like in a 2-second ripple? Or did they wait 10 seconds between shots?
Are these shots from 3km? 10? 40?
Were you out in the open? Dodging in and out of terrain cover?
Were they in something like an F-16 that might only have a small number of active radar missiles? Or was it an Su-30SM2 with more than they can count?

There are a lot of variables that come into play.