When do you replace equipment due to issues?

Brief background:

I've been through several network equipment changes over the last 10 years and now starting to wonder if it's time to switch again. We started out with HP Procurve in the beginning and then went on to Brocade, followed by Aruba. The last two changes have been due to issues which affect production adversely.

Now we're starting to see a lot of bugs and it feels like I'm upgrading switches every two weeks because of it.

My question now is when you think it's time to move to new equipment/vendors because of issues?
When is it the "last straw" so to speak?