We recently received three estimates for painting the exterior of our house. One of the contractors said we needed to replace all the wood siding on one side of our house, and part of the siding on another side. The other two did not mention replacing siding.

How can we tell if we need to replace the siding? It has some sun damage (cracking), but isn't rotten or coming off or anything.

I would start by asking the other two estimators how they would address the cracking. If they have a plausible plan for fixing the siding cracks then you will be better informed and can make your decision. Bet those 3 estimates were all over the place.

One suggested using oil-based primer to seal the wood, and the other suggested using caulking in the cracks.

If they are willing to do both primer and caulking you might have a good plan. They should also explain if they are power washing or scaping or sanding the bare areas. Try to pin them down a bit about their techniques. Do not assume anything if they haven't given it to you in written proposal.

Siding is sometimes called weather boarding. In addition to pleasing the eye, its main function is to keep the sun and rain off the sheathing. It is the sheathing, not the siding that keeps cold drafts, crawly things, etc. out of your house. So when it comes to replacing your cracked siding, you need to decide if the improved appearance is worth it to you.

I do have to add that I ripped the old, deteriorating hardboard siding off my house over 20 years ago and put vinyl on. I have no idea how many times it would have needed paints since. I have never regretted it.

The direction you go, relative to the maintenance of the exterior wooden siding on your house, most likely will be based on two things... your budget and/or your desire to maintain the original materials/character of the structure. You can bet that whatever method you choose... to maintain the condition of the wooden siding (wherever it is)... will require addressing the same issue in the future. If you are able at this time, to replace the existing wooden siding... As Labman has suggested... You will be glad you did.