Does traditional CO2 laser resurfacing permanently thin the skin?

Yes, the skin heals after Co2. Fraxel or Co2 are best for resurfacing. I always combine lasers with microneedling/prp, Sculptra, peels, fillers and rf treatments for more robust outcomes for facial rejuvenation. We space treatments every 4-6 weeks, but will depend on healing. I recommend getting a formal evaluation with a cosmetic dermatologist. Best, Dr. Emer

Over time, skin tends to get thinner actually. The laser rejuvenates the skin, increases collagen, and increases the natural "younger" architecture. Studies have shown that experienced pathologists (who study tissue samples under the microscope) will get "fooled" by lasered skin as it will look actually like skin from a much younger patient. The ablative CO2 resurfacing is still the gold standard for treatments, with fractionated treatments having a smaller effect (in exchange for smaller downtime). It is always best to make a consultation with a board-certified expert who can explain all of your options.

Actually, the CO2 laser helps thicken the skin!  I works by taking off the top layers of the epidermis which would make you think it it thins the skin.  However, the stimulation to the deeper layers (the dermis) by the rapid turnover of the epidermis and by the heat deposition by the laser in the dermis, causes collagen to be formed in the dermis.  This new collagen formation is what helps improve acne scars and minimize pores. 
The top layers (epidermis) are constantly turning over meaning the cells die off and get pushed to the top later to be sloughed off.  Thinning the epidermis is a temporary effect of the laser--its basically burning off those dead and dying cells.  These cells are constantly being replaced so taking them out of the picture a bit early is not a big deal. 
There can be problems when the CO2 laser is used too aggressively and takes off all the epidermis and injures the epidermal-dermal junction where the new epidermal cells originate.  This can cause permanent problems.  Just be sure you go to someone who is familiar the CO2 laser and regularly treats patients with this modality.  Used correctly the CO2 treatment can work wonders! 
Hope this all makes sense!  Best of luck,
Dr. Amy