I see many who drop the facial covering (not all use actual masks) down to their necks and raise it back up when need be. Since a kerchief is an acceptable covering - this should not be difficult .... especially when the purpose of the mask isn't to keep you from getting the virus, it is to keep you from spreading the virus - so, puting it off and on should not cause any additional risk to you ... unless you are getting so close to those without a mask that they are "breathing/spitting" on your mask.It is not a good idea to repeatedly take the mask off and put it on
By keeping the mask on all the time can oversaturate it with moisture from your body and partially defeat the reason you are wearing it ... so, taking it off and on will help keep it drier.
BTW - That's why I carry more than one mask - we made our own since buying them was problematic, at best. When I go into a public building, I put my mask on. I DO NOT touch my mask or my glasses while in the store if I can help it. I do carry a "disinfectant wipe" with me incase I do have to touch my glasses and clean them off before putting them back on. When I get back to my vehicle, I clean my hands, keys and door handle with a new disinfectant wipe before I remove the mask.