Carbonation Seems to Increase After Several Months

I've had an interesting phenomenon happen to me with several beers that haven't been as popular so they hang around a lot longer. After 8 months or so in the bottle, a few of my recipes have become excessively carbonated. They foam over as soon as I pop the cap and while I pour but don't seem excessively carbonated when I drink them. Wouldn't be an issue except that I lose about 1/5 of the beer to foam. Is this just something that happens to older bottle conditioned beers or is there something I can do to correct this?

I've got a buddy who this is happening to, but it was more like 2 months instead of 8. In his case, it all foamed out... It turned out that it was most likely an infection of some sort that caused his. How does the beer taste?

They taste pretty much exactly like I meant for them to. I don't think it was an infection because of the long length of time before it happens but I won't completely rule that out.

gushers are usually infection related.