In general I agree with David, but in your question, Michael, is a crucial point.
Clothes moths, as we all know, seek and thrive on three things: darkness, humidity, and undisturbed air (apart from the animal fiber food source, of course). So if you're going to store woolens, cashmeres, mohairs, and silks for at least one spring-through-fall cycle under circumstances that don't allow you to open the container, brush out the clothes, and replenish the volatile oils in a repellant (e.g., cedar oil or the like), the only truly reliable way to prevent moth damage is to fully seal the container, and incorporate a moth-killing product.
Adult moths can crawl through crevices so tiny you wouldn't believe. No garment bag with a hanger opening will be fully mothproof, and often the end of the zipper attachment has enough space for a clothes moth to crawl through. Even widely spaced seam stitches in some bags are vulnerable.
So during the warm season I store my tailored clothing in lightweight breathable woven nylon clothes bags with zippers and hanger openings, and I slip a rectangle of heavy blotter paper saturated with essential oil of North American red cedar over the hook of the hanger (having used a hole punch to allow the hanger to pass through) so that the bag's hanger opening is largely blocked by this strong moth repellent. BUT since I know this is not fully mothproof, every couple of weeks I open a few of the bags, lightly brush out the garments to dislodge any moth eggs or tiny larvae, replenish the oil on the blotter, and close the bag up again. This way I work through the whole wardrobe two or three times a season. If the bags are hung adjacent to each other, the volatilized oil from the refreshed bags will help make the general area unattractive to moths. And the cedar aroma is quite pleasant, and dissipates quickly once the garments are back in use for the cool season.
What I do for woolen sweaters is to fold and stack three or four, separated by tissue, together, and seal them in a clean white plastic trash-can liner bag for storage in drawers. I use
these small but very effective moth-killing, EPA-approved paper sachets (active ingredient is the usual paradicholorobenzene, but with a very mild cedar scent) tucked between tissue in the middle of each package. I either twist the package closed with wire ties, or seal it with clear package sealing tape. Once cool weather arrives, I remove the sweaters from the bags, unfold and air them, and then refold and store uncovered in the drawers.
The only caveat is that using a relatively impermeable package (such as plastic trash bags) will contain the moth sachet vapor well, but will also impede the movement of water vapor. So if you seal the package during very humid weather and store it for a long period in warm or highly fluctuating temperatures, you risk mold formation. I've never had a problem with my sweaters using this method, but they only stay sealed for four or five months in relatively stable temperatures (sudden changes in temperature can lead to condensation which is the usual trigger for mold/mildew).
So there's a tradeoff if you need to store your tailored woolens for longer than a season. Breathable coverings will resist dust and light damage, but cannot guarantee full protection against moths. Sealed packages (bags or plastic storage containers with perfectly sealing lids) will be mothproof (I store my unmade LL cloths this way, too) but must be stored in conditions that don't promote mold.
David mentions storage at cleaners. The reason such commercial "cold storage" for furs and off-season woolens is effective is that (if responsible) the facilities are kept well below 60 degrees F, and at humidities of 40% or below. Mold will not grow under these conditions and clothes moths (and other protein-fiber-eating insects) cannot survive long at such low humidities. So if you need to store tailored clothes for longer than a season or where you can't monitor them, this is good insurance if you have access to a facility whose storage conditions you can be confident about.
In the days of valets, the daily or weekly brushing was all that was required, and hanging in an open wardrobe was fine. Clothes moth eggs are very lightly attached and brush off with the mildest handling of the garments. It's the necessity of frequent and regular handling/brushing that is so difficult to maintain today.
