In my 1999 Civic EX, I took it out at 125k miles (6 yrs) because I was not comfortable going longer on it. Manual does NOT have a change interval, so YMMV. I cut it open and the cardboard (brown) paper element looked like it was lightly dusted with grey/silver on the dirty side compared to the clean side. Hard to say by looking at it whether pores are plugged or not. Certainly no big chunks. Service manual had a pressure test to determine if filter is OK or not. But for the $15 you spend, and the 1/2hr time it takes to replace this, why not do it? 100k miles is a good time for a new one IMO (if it is serviceable). Anything shorter would be an OVERKILL for sure. Until then, don't sweat it.