This is quite a common procedure in the market you're talking about, since most operators don't want to fork out for a proper runway analysis for each trip - apart from the short notice time constraints.
As to it's advisability, there are two factors here.
1. Your a/c may or may not have figures in the manual for extended climb. Certainly the CL604 does and the 601 doesn't. If it does you can use those to get an accurate figure for speeds/gradients up to whatever accleration ht. If you haven't extended climb figures then you need to use the speeds and gradient for the end altitude, which is conservative. Either way it not a certification problem.
2. Look up the distance required to accelerate OEI at high weights, and then decide if you want to fly around below MSA in cloud in an unfamiliar area for that number of miles!
After that I think you'll find it's the sensible option
