So we're at GF 31, only 69 (nice) more to go. Which at this rate will only take about 12 more years. Also this reminds me of that LN story where Rentarou stayed up for 24 hours going on dates with at the time his 8 girlfriends, so imagine 31 now, but knowing Rentarou he'll make all the time in...
So we're at the 30th girlfriend, meaning we're 30% through the manga. It took us 5 years to get here and at that pace we should be done in about 11 more years...
Do you think the author will add anymore to MC's harem, that's probably the only way for this to get interesting again. That or maybe actually develop the relationship MC already has, which is a lot to ask for in a harem manga.