Do they bloom through summer and how often do I need to feed them?
Do I Pinch Dianthams Dead Flowers Off?
Certified GKH Gardening Expert
There's no need for pinching, though doing so will not hurt the plant. Yes, they will bloom throughout summer. You can apply a balanced fertilizer every 6-8 weeks or simply use a slow-release fertilizer at the time of planting, along with some compost. This should be sufficient and lessen the need for you to continually do it.
Also, deadheading is often a good idea once the blooms fade, as many varieties will self-seed. If you don't want them popping up in unexpected places, this will help. Otherwise, you can let them be and allow them to surprise you with additional plants.