My monitor is taking longer and longer to power up - sometimes as much as three or four minutes. Seems to be okay, once it gets started. Is this a sign that it's on the way out? Thanks
Can you please clarify what you mean by "power up" in this instance? Are you meaning you press the power button on the monitor and nothing happens (e.g. no LEDs light, no display, etc) and then spontaneously after a few minutes it turns on? Or that you press the power button and LEDs/power indicators light, but the image either does not display, does not display brightly, or does not stabilize for a few minutes?
Also, what kind of monitor do you have? Is it an LCD? A CRT? A Plasma? A Projector? etc
Overall this is likely an indication of problems if the device previously started quickly, however depending on the display type it may be less worrisome. If it's an LCD taking this long to bring the backlight on, for example, that's a big problem, and the device is not likely to last much longer. CRTs, however, can sometimes take a few minutes to stabilize the image, especially if your climate is very hot or very cold, and it may simply be a matter of moving the monitor somewhere more regulated or waiting for the seasons to change. However if it is a CRT and its producing error messages on start-up (e.g. a Sony Trinitron throwing HV-test fails) that too indicates potential future failure. If it's a projector and it is taking a while for the image to come up, it may simply need a new bulb, or to have a presentation blanking mode cleared.
With more information I can likely provide a more directed answer.