Anti freeze doesn't evaporate, water does. Adding a small amount of distilled water to top off the reservoir won't hurt. It never hurts to have the coolant freezing protection checked at a service appointment, just ask for it. Repeated frequent loss of coolant suggests a hidden leak if no drips are evident and should be checked with a leak detector dye by a qualified mechanic. After any repair the antifreeze lost must be replaced with the proper type to achieve the correct 50/50 ratio.
As to the addition of methanol, I suspect that the main cause of that error is topping off the coolant reservoir with windshield washer/anti freeze fluid. That might call for a pre mature coolant drain, flush and fill to prevent damage.
Much of the coolant in use by garages now is recycled. That is coolant that has been drained and stored, filtered to remove dissolved metals and other unwanted particulates, acid balanced, a new additive package added to restore lubricity and anti corrosive properties then corrected to 50/50 ratio by adding new product or water as necessary. It is environmentally sound recycled and green but and a big but, it is not factory approved coolant. We used it in my garage, it is great for a 15 year old F-150 but not a newer Asian, European or late model American car especially if there is any possible warranty. For those, at a much greater expense we stocked a case of genuine Toyota brown coolant and GM Delco factory coolant as well as Zerex. With a 100,000 mile warranty, make sure you are getting the proper coolant installed if you need service!