I have a publisher who wants me to write faster and says they want my future books. Is there any value in me trying to "upgrade" or should I just be grateful that someone wants to publish me?If you have a publisher who loves you and wants more of you, why in the world would you want to leave them?
The only reason to even consider switching publishers is if they're not doing a good job for you—or if they're a small niche publisher and you want to go national.
Are they targeting your maket? Do they pay you a fair royalty? Are they promoting your books? Are your books selling well? If so, stay where you are.