Ttc but shouldni be done?

My husband and I are currently ttc baby #3....this month I decided if I'm ever going to have baby #3....it's now or never....I had baby#1 a girl (2004)2 weeks before my 24th bday. When she turned 1 we decided to try for baby # 2....it took a long a long six years (2010) my husband and I have both always wanted 3 kids....at the age of 34 I'm wondering if it's a good idea or not for me to have another baby....I realized I only have a few "good" years left and have a daughter whose 10 and a son who will be 4 on Tuesday.....I'm going for the "if it happens it happened" Approach

.....not doing the craziness I did to get preggers with my son....I'm just curious what age u all think is to old to be trying. At this point should I just be happy and content because I have a daughter and a son????