I am assuming you are controlling the servos directly and not using a separate servo controller ?
An SD21 servo controller gives you an option to set a speed register but that is over kill if you are using 2 or 3 servos.
The example used in the SD 21 documentation to explain the speed is shown below, but this handled by the servo controller
The servo pulses are automatically refreshed every 20mS. If the Speed register is zero (0x00) then the servo is simply set to the requested position. On power up the Speed registers are set to zero to give full speed, so unless you need to slow them down the Speed registers can be ignored. If the Speed register is set to something other than zero then that value is added to the current position every 20mS until the target position is reached. If you wish to move from 1000 to 2000 and the Speed register is set to 10, then it will take 2 seconds to reach the set position. The formula for the time it will take to make the move is:
((Target position-Start position)/Speed Reg)*20mS
Here are some examples:
Start Position Target Position Speed Reg Time for Move
2000 1000 10 2000mS (2Sec)
1000 2000 10 2000mS (2Sec)
1000 2000 1 20000mS (20Sec)
1000 2000 100 200mS (0.2Sec)
1234 1987 69 220mS (0.22Sec)
Basically doing what your loop does but the load is moved to the servo controller.
This post may help http://arduino.cc/forum/index.php/topic,21975.0.html It is titled Servo timer so it may have the functionality you need.