As Blue Emu implied, the annual failure rate is a VERY misleading number. A much better number to look at is the expected time to consume all maintenance supplies.
The reason for this is that the annual failure rate is proportional to the tonnage in your ship (or your navy). Imagine 10x10KTon ships, each of which has an annual failure rate of 10%, and a 2 year expected time until it runs out of supplies. The annual failure rate of the squadron is 100% (10 ships at 10% each), but the squadron as a whole is still has a 2 year expected time until it runs out of supplies. Components are failing 10x as fast in the squadron as a whole, but there's also 10x the maintenance supplies. Now consider a (approximately) 1x100KTon ship designed by taking the ship design above and multiplying the quantity of all the components by 10x. This ship will have a failure rate of ~100%, but will have an expected supply time of 2 years.
In other words, the annual failure rate will be proportional to the mass of the ship, and should be ignored. The expected time to consume all maintenance supplies tells you when you'll actually get into trouble with supplies.
John