I'm considering studying for the CCNP. I am not a network engineer, I am a programmer, but the field where I work with is incredibly closely related to networking and if IOS/API ever comes to light having a CCNP would probably open some doors. Plus I like networking in general

Anyways, some questions before I decide if it's worth the time commitment:
1. How long do you have between each of the four sub-exams to pass another?
2. Once you have your CCNP, how hard is it to keep? i.e. is there a very easy 622- exam you can retake every three years (no intention of getting a CCIE) to keep the cert?