So when we replaced our roof a couple of years ago with a 20 year roof I figured out what we’d have to save to have enough in 20 years to replace it. Granted, living on the gulf coast with hurricanes, we’ll have to replace it sooner. Hopefully insurance will cover part of it and we can use whatever we’ve saved to go towards the deductible. So for now I am putting back $50/month. I know costs will go up in the next 20 years but I figure we’ll be pretty close.