I live in the Seattle area and had cedar shake roofs for over 30 years, so I know what you're facing. The problem with a 15-year old cedar roof is that you are going to have problems in other parts of the roof in the not-too-distant future, so whether you get the cheaper job or the more expensive one you're just putting things off a little.

Unfortunately, shake quality is poor these days because the shakes are typically new growth, which rots faster. After going through two cedar roofs and being at the point of needing a third, I decided that a 50 year, non-leaking steel roof was what I wanted. I love the look of cedar shakes when they are new, but the continuing maintenance is just a drag. My suggestion is to consider getting either an entirely new architectural shake roof that mimics cedar but will last a lot longer, or go to a steel roof. There is a lot of comfort in not having to continually clean off, worry about, and repair one's roof.

I agree with kudzu9. Cedar is a very pricy roof and for similar pricing, you can have somthing that you don't have to worry about every 10-15 years. Steel is the way to go. Or even high quality asphalt architectural shingles. Check with your insurance company about possibly receiving a discount for switching from cedar to steel. Some offer that because of the greater fire resistance. I don't think Seattle has issues with wildfires like SoCal, but it's remotely possible that your municipality might also offer incentives to switch to steel. It's worth a phone call.

They make steel roofing to mimic shakes and from a short distance one would be hard pressed to tell the difference.

If you already have deteriorated shakes, just walking on the roof to repair them is very likely to cause more leaks (or At least damage more shakes).