Guys in their mid 30s - 40s will normally take about 10-15 hours longer than the minimum, sometimes a little more. Can't tell you much without sitting next to you but normally there's a something that holds you back, with guys who are business types that have reached reasonable levels it tends to be them being too hard on themselves and being impatient. You can often hear them saying
"Eff it I can't do this, you have control"
If you're frustrated you may well be in this category, just be patient and keep talking to your instructor about what's next. Also keep practising your skills, slow flying, stalls, steep turns and most importantly forced landings
. Do one or two of these on your way back from the Nav.