When should blinds go up?

[jdAA88]

Me and my friends usually play a home game every week with about 6 players in total.
The buy-in is usually $20 with blinds starting at $.10-$.20...then after about 45 minutes we usually raise them to $.25-$.50 but after that no one usually wants to keep raising them until there are only 2 players left.

Is there a certain standard or average when it comes to the blinds going up and also how much they should go up by?