Don't know about your spot on this globe but up here (Latitude: 47.606) it's pretty dark at 4:30 and the ski resorts are all open. Time for some seasonal service for those wood wheels I ride all year.
Wood rim wheels are low maintenance, but it pays to give everything a good look over at least once a year. Here are your tasks:
(1) Dismount your tires
Once a year, remove your tires (unless they're tubulars and the tires fresh) and inspect the wheels, inside and out. Look for anything abnormal. If a wood rim is going to delaminate, it's probably because the wood glue is failing. Before the era of epoxy, glues aged and eventually turning to dust. Such a condition can, on close inspection, be detected long before the rim actually splits. Nipples and the compression loads that spokes create in the rim both act to hold a delaminating rim together. But it's a bad idea to continue riding such a rim, which is still fine for display.
If your wood rim is wider at any point, look very closely. Wood can warp but it doesn't become thicker without cracks. Besides delaminating between plies, wood can develop cracks that would make the rim section wider. A rim could split down the center, from spoke hole to spoke hole. Beginnings of such a split should be visible with the tire removed. The valve hole is the most likely place for a crack to start since it's the largest diameter hole. This unlikely condition is easy to guard against.
(2) Check your tension
The shaped washers that support each nipple tend to settle into the wood for the first year or two. So, expect a noticeable decrease in spoke tension. I've seen tension halved in the first year.
Easy solution: put 1/2 to 1 full turn on each nipple to bring tension back up. Don't exceed 70kgf, your wood wheels don't benefit from highest tension. The point is simply to keep the tension up in the 40-70 range. Remember, wood rims love some freedom to move, to respond to road bumps, to absorb shocks. That freedom comes from moderate (reduced) spoke tension.
Aluminum rims hate movement. They are rotten at absorbing shocks (as are aluminum frames) and accumulate fatigue with every load cycle. The solution (for rims, frames, or planes) is to design so there's no flex. That minimizes metal fatigue but works against shock absorption and feel. Not so with wood.
(3) Clean the brake track
With the tire removed, you can scrape accumulated (melted) brake material from the rim side. Don't worry about a black stripe that seems to be pure color (no deposit) because that's just a burn mark. Melted brake pad material can be scraped, rubbed off with Scotchbrite, or loosened with alcohol. It's not necessary to restore the rims to unused condition. Don't try to rediscover the untouched beauty, the wood is happy to be a rim and show off badges of its occupation.
(4) Recoat obvious bare spots
As with a boat, use a sealer like polyurethane varnish or clear nail polish (for small knicks). It's definitely NOT necessary to recoat the entire rim. I ride mine in Seattle weather and they seem immune to moisture damage. Just try and avoid sudden changes in humidity. If you ride often in the wet, then store your bike in a cool room with outside humidity. I know plenty of riders who break all the rules and seem not to suffer. My tips are just suggestions, not care instructions.
Weather can be a cycling challenge
(5) Inject epoxy in holes
In case you find damage from boring insects (we're talking about ancient rims), make sure they've left and inject epoxy down any holes. Substantial pressure from a syringe will seal the holes and related deterioration, leaving the rim much stronger. Insect damage is rare and will only appear if a rim is stored for years in a dirty basement or barn.
(6) What about small cracks?
For tiny cracks, use CA (super) glue formulated for wood. These adhesives are incredibly strong and can wick into porous areas increasing strength. I'm a fan of "Hot Stuff" instant glue and its aerosol accelerator:
Small cracks are rare, but easily fixed.
(7) Expect to do a bit of truing
Wood is not "alive" in the biological sense but it's certainly alive in the dynamic sense. Wood responds to humidity and temperature more than metals. You may find your wheels need a small truing touchup at the beginning of Winter, after temperatures turn cold, and at the beginning of Summer, when it's warmed up and drier. The rims are not suffering or deteriorating, only responding. I recommend being a little lazy and let them run a bit untrue. Makes it easier on everyone.
(8) Ask questions
The Cermenati family, makers of Ghisallo rims, and I are eager to help you enjoy wood rim riding. Neither of us has all the answers but we enjoy the blessing and challenge of riding on wood. Ask questions and share your insights.