Using shutter mode simply closes a shutter over the still on and working bulb, so I wouldn't recommend this for any length of time at all ( < 10 mins ) because you're still cranking up the hours on that bulb. Equally when the shutter is closed is there a greater chance of the lens enclosure heating up ????
General rule of thumb is, once you turn on the PJ make sure you're going to be using it for a couple of hours. Turning it on then off shortly afterwards is not good for the bulb. Equally once you turn the PJ off make sure its turned off for a good wee while as well because turning it on again ( say within the hour - confirmation anyone ?? ) in a short space of time stresses the bulb.
Most on here who have an AE700, myself included, hardly ever leave it in standby. The reason is most people tend to see Vertical Banding once they have done so and need to go into the settings to implement the flicker tweak. Actually turning the PJ off, after proper cool down period of course, reduce this dramatically.
Something to bear in mind
Regards
KH