I bought a non-Insight car with 139,699 miles on it where the previous owner said he didn't touch the manual transmission oil, I checked the fluid level through the fill bolt by sticking my finger in there as far down as I could reach, came out dry. Before draining, I figured it wouldn't be too bad, but when I did, it looked very gray with metallic glitter. I was freaked out by this so I filled it back up with the manufacturer-specced 75w90 gear oil and figured I might need to swap the transmission in the near future. The next time I changed the oil I went to drain it again in order to see if there was leftover grit or metal from last time, or see if the transmission was tanking even more. To my suprise it looked as good coming out this time as it did going in. The next year before winter I changed it again and it was still looking good, same with the year after, came out clear. I'm not sure if it was due to a bad driver wearing out the synchros or what, it wasn't metal shavings or grinds but a very fine material. Either way I imagine that the stuff could possibly be abrasive so I'm glad I got it out. 74,000 miles later and that car hasn't had any issues, clean fluid, shifts great, no noises, but if I didn't get that crud out, I figure the transmission wouldn't be in the same condition.
Your mileage may vary, especially with a different car, the car that I'm talking about specs no change interval if I remember correctly if it fits very specific highway driving criteria, but after seeing what I saw this car it has been getting the severe service 30k changes so I hopefully never see that again, but with a different car I'd probably go with the standard interval if things checked out after the first severe interval check, but I like to spot things before I notice a problem, at least a finger dip in the fill plug to check the level and see if my finger has anyting gray on it.
Personally I'd go with the 60k schedule if your driving involved city use(lots of shifting and more input shaft rotation versus output shaft rotation) or isn't largely highway miles(lots of miles with minimal shifting). I drive to work and back 30 miles total and I shift only 25 times if I get one red light, which is usually the case. I'd shift 40 times if I got all red lights, even more if I run into traffic, which I never do. So my transmission oil and synchros are not very stressed IMO, far less than someone driving in stop and go traffic, possibly shifting hundreds of times in an hour.
--On a side note, there are a few people here that have mentioned synchros wearing out leading to grinding shifts, another reason to keep tabs on the oil, especially if downshifting often or have a habit of forcing shifts instead of using moderate pressure and letting it slide in. Fluids often don't determine synchro life, but rather their treatment, yet I still think that signs can be found in the oil of a MT that can let you know something is up. Again, Your Mileage May Vary.