Doing a quick stability test takes little time and effort compared to the amount of information you can gather, as long as you can correctly interpret the results. Doug Chabot (Director of the Gallatin NF Avalanche Center) and Mark Staples (Avalanche Specialist at the GNFAC) have written two excellent articles on the importance of digging for February issue of The Avalanche Review. These articles are posted on the GNFAC website here and here. Check 'em out!
It's important to remember that you don't need to take a long time to do a stability tests. If the layer you are testing is not very deep, you can do a stability test under three minutes, as demonstrated by Mark Staples in the video below. Heck, Mark did it in about two minutes, including taking off his skis!