HWB - Are you sure about this, or is this something else you have been "given to believe"?
The qualification period for the Operation Service Medal for Afghanistan is not six months, but varies, with 30 days continuous service being the usual length of time in most cases. Service curtailed by injury or death counts for the medal.
Waiting a few months for a campaign medal is hardly worthy of comment - the issue of WW1 and WW2 campaign medals did not start until several years after the end of hostilities in both cases.
All that said, I agree that MPs shouldn't be getting a medal for flying in for a quick photo opportunity, if indeed that is happening.