I had that exact situation, but a bit worse. Parked the bike and noticed a screw in the tire. Took the screw out, checked for leaks - very small amount goes out, but it's an air leak. So, I orderd a new tire. A few days go by, I check for leak again, and... no leak. I guess the rubber restored its original position and sealed the leak. So, I got a small piece of rubber, lubed the hole with rubber glue, and stuck that piece of rubber in there. Rode on that tire till it was worn out.
I do have a TPS on the bike, so it was easy to keep an eye on the pressure. Without it, I would've felt less comfortable. But by the same token, if you go for a day's ride and puncture the tire at some point, you may have a significant air pressure drop shortly thereafter, and you may not even know until it's too late.