This article is from the comp.sys.ibm.pc.hardware.video Frequently Asked Questions, by Michael Scott with numerous contributions by others. (v1.0).
There are parts in the monitor which may get hotter with SVGA but if it is designed for SVGA resolution, there should be no problem (assuming you are not running in an excessively hot room or with the ventilation holes covered).
A good quality multisync monitor should not mind switching screen resolutions frequently (though doing it every few seconds continuously may stretch this a bit).
Newer multisync monitors should also be smart enough not to blow up if you feed then a scan rate which exceeds their capabilities. However, there are a lot of poorly designed monitors out there.
If it is supposed to run SVGA, use it at SVGA. If it blows up, switch to a different brand. There are a lot of crappy monitors being sold on their own and bundled with PCs.