Or maybe he is more accurate than you are, thus reducing the number of off-centre hits and extending the strings' life
Well, 1 month is way too general. We need to talk about the actual playing time. I can say it last for 1+ yr, if I can play 15 min a week. Or, I can say, it last only 3 days, if I do 10+ hrs per day.
I play about 3 times a week, for 2 hours each session. Been playing for 5 years now. I usually hit the bird dead on. I think i am a farely hard smasher, i just don't go smash every bird i see. I use drops more than smashes to be honest. So maybe that will last longer. btw its strung 22lbs on a mp77sp
I'm currently using Gosen Pro66 .66mm. The reason why i love this string is that it is cheap and can retain the tension longer than other Yonex thin strings. Since i strung it at around 27lbs to 29lbs , i find it more durable and good feel for that string. Besides Gosen.. i also like to use bg68ti. Durable but tension doesnt not last as long as pro66. Bg65ti is good also for me.
For me, it's Gosen Biogut Bioroots strings. I think there are three versions, I've seen three. I have the Bioroots which is 0.72mm thick and there are two others, Bioroots 68 and Bioroots 70, with thickness 0.68 mm and 0.70 mm respectively, I believe. The Bioroots (0.72mm) I have on my Cab 30MS right now and they are great; for a thick string, it has great repulsion as well as control. I will try the other strings sometime, I expect it to be soon, as well as the Biogut Aermet strings too.