Each extra comma tells you modem to sit and wait a second before attempting a connection. If you are having trouble staying connected it could be a number of things. Possibly the phone line, the modems involved, or both. If you notice any noise on your phone line, please call your phone company and let them know that you hear line noise when making voice calls. V.90 is relatively new.
Some modems are extremely agressive about connecting at the highest possible speed.
This sounds great in theory, but in practice can cause problems. The reason is becuase the modem may actually connect faster than it can reliably send and receive data. When this happens, you connect up nice and fast, but then get lots of stalls and or disconnects. This will cause the modem to not attempt to negotiate a full speed connection. You can set the maximum connect rate by adjusting the last number.