I thought to add my 2cents worth. I currently own 2 G-shock watches. One is seriously old. Model DW-5700. One much newer, Model DW-5600E. The old one survived through about 3 years of high school and 5 years in the army between my brother and I. 2 sets of BMT, armoured engineers/pioneers, OCS, jungle training, etc. It was really tough. The watch face is still unscratched, though there are some dings in the metal back plate. It still looked pretty good after I left full time service, but after 3 more years of civilian life, the rubber armour around the watch finally broke in a strategic place that left it unanchored to the rest of the watch. The new G-shock was bought recently to replace it.
This is the one weakness of the G-shock. And, I guess, of any rubber armoured watch. It is susceptible to DEET, an industrial solvent used as the main active ingredient in some of the most effective bug-repellents. But the watch is still in such good condition otherwise that I'm still looking around for a way to replace the rubber armour. Anyone know where I can get one? (please email me)
So, the G-shock is a tough watch, no doubt about it. You should get many years of useful service out of it. Just watch out for the DEET.