nice info... will need that sometime very soon with my current proj but is it advisable to use it?? i mean there r no side effects i guess !!
ini_set() is the powerful function provided by the php, so it's effects depend upon the hands which use it.
The fairly time consuming may exaust your live database completely if executed with setting max execution time to very high value,
or else it can prove to be a boon when you need to change this parameter over just single script, and it last until the script execution completes
So the conclusion is its you, who decide how to use it.
Edit : the nice explaination about ini_set() here