It is the duty of the husband to fulfill wife's every sexual desires. If you don't she might look for someone else. I understand you'll get bored and sick of sucking the same nipples everyday, so you have to be creative. Try adding some flavours to her nipples and suck it.., for example honey, whip cream etc.
Some suggestion for you...
1. Monday - Honey
2. Tuesday - Whip Cream
3. Wednesday - Ketchup
4. Thursday - Chocolate syrup
5. Friday - Red / white wine
6. Saturday - Salt & pepper
7. Sunday - Rest day for you