All of my NCT group are in the 36-41 age range. All had their first children without any fertility treatment and within a year of trying. Half are now expecting their second, again without any fertility treatment.
Fertility is affected by a number of factors, age is only one of them.
If you're sure you want children then what reason is there not to start trying?
If however you're unsure, then think very carefully and don't feel pressured by society or by fertility headlines in the press. How does your partner feel?
Imagine giving up your current well paid job because it doesn't cover the cost of childcare or because the hours your employer expects you to work don't fit with childcare.
Imagine doing a job, 14 hours a day, 7 days a week, with no holidays, no sick leave and some night shifts thrown in, for several years. Some days you love that job, some days you hate it. But you have to do it everday however you feel.
Imagine this job dictates where you live, where you go, who you spend time with, what you spend your money on and how often you talk to your partner.
If none of that fazes you you're probably ready :)