NMB has high boiling point of about 200 C, and the evaporating process should be done at relatively high temperature which would affect graphene flakes and properties.
If you can withstand this properties modulation you can try 140 or 150 C for 24h.
I think this kind of drying process may cause agglomeration of your exfoliated graphene. It will be better to keep it in the NMP for a week or two and separate the supernatant liquid for future use. If you need bulk amount graphene, go for centrifuge, as Dr. Roy suggests and for less amount try to transfer that may be by spin coating, dip coating and any other.