I have a 2008 Kona Blast (aluminum frame) and lately I noticed that the rear wheel has become very difficult to get on. To get it back on, I have to really loosen the quick release to get it to fit and then re-tighten it by hand while squeezing the dropouts together. It appears that the rear dropout width has slowly expanded over the years. When I measured the distance between the insides of the dropouts it was over 141mm while all of my other bikes measure around 137mm.

Luckily, I don't have to take the rear wheel off very often, but is this something I should be concerned about? Is the frame's integrity at risk?

Any input would be appreciated. Thanks.