Great report Brian. As your last paragraph reads one of the most important aspects when selling and installing turnstiles that are mounted outside is the maintenance. It usually takes a few years before these start breaking down but you can extend the life quite a bit by following the manufacturers recommended maintenance schedule. Considering the high cost of installing a turnstile it is much easier to get the customer to purchase a maintenance contract, at the bare minimum a preventative maintenance contract to keep their turnstiles in working order.
By checking the turnstiles on a regular basis you can find small deficiencies and repair long before the issues turns into a massive repair bill. For instance the bearing at the bottom of a turnstile isn't very expensive but the labor to replace can be. So thereby keeping the bearing lubricated will help tremendously.
If you are selling these also consider keeping a re-built kit on hand as well. One is the kits are typically less expensive than buying individual parts and two you have what you need for a service call.
We have sold quite a few Alvarado turnstiles over the years, both indoor and outdoor. Their help with the pre-sales support, installation support and service support post install are second to none in my opinion. There are other good turnstile manufacturers as well but we just happen to lead with Alvarado.