Whether you are a provider or a hobbyist, perhaps the best way to watch a clock, without watching a clock, is to have a number of one hour playlists programmed to fit a number of moods and tastes, and be familiar enough with the playlist to glean some knowledge of how much time has passed and whether you need to "manage" the session to get to whatever activity you may not have done yet that you really want to fit in.
I now carry in my kit (there is a thread somewhere on Anon's ultimate outcall/incall kit) a small speaker system for my Ipod, so I can use it regardless of incall or outcall. If it is an outcall, i already have the stuff set up. If it is an incall, I show the lady what is in my bag and ask permission to set up as we chat. This usually involves getting the refreshments and candles out (if she doesn't already have a nicely set up incall) and setting up the sound system. I usually have the play button going within a minute or two of entering the room and laying the donation in an envelope on the table or dresser.
This helps measure the time in a subtle way and helps both parties get down to business without the abruptness of disrobing as soon as she latched the door, and still provides a mood and atmosphere conducive to the GFE.
No feelings get hurt over one of the more touchy and perplexing issues of little this hobby of ours.
In my old age, MSOG are rarely an issue--in fact I have to worry about cumming the first time. For whatever reason that seems to work best during a BBBJ
AFTER I have gotten her off via DATY or CFS. On every playlist, I have a song that plays that is my cue to get her off one more time doing whatever we happen to be doing and try to transition back to a BBBJ, leaving enough time for a skilled provider to do what works best to achieve the goal I most wanted.