How long, it depends on how much studying you do and if you are working or not. But normally there is a reason why Cisco renews older certs automatically when you take new ones, in part its because they want people to take new certs, in part, many people also plans for not doing more than one of the higher levels each ears. So from after getting CCNA/CCDA and going to CCNP/CCDP would be one year, but its quite alot to read and test for, and unless you have a employer that pays for your testing, you have to consider that part too... after that, its probably at least another year if not more if you cant study full-time to CCIE level judging by the CCIE's I know so far.
The CCIE is a multiple-day exam with like 9 lab components or some insane nonsense. IIRC it requires a bunch of experience in the field as well. There's a reason a CCIE is worth six figures. CCNP shouldn't be too hard. If you apply yourself you should be able to get the CCNP by the time you graduate by studying outside of class-- heck, I did half of the CCNA my senior year of high school, no reason you couldn't push through it in a good bit less than four years.
Yes and no. Up until the practical tests, you can actually study it up to a CCIE without that much pure cisco experience. A colleque at work actually has CCNA, CCDA, CCNP, CCIP, CCDP and written CCIE(R&S). Has he ever worked in a live cisco envirorment... nope. Has he rented a lab and studied a whole lot... quite so. But then, thats probably more of an exception than a rule. That said, he missed the two first tries at the practical tests of CCIE(R&S), which I woud chalk down a whole lot to the lack of practical experience. But he does have experience with Nortel and Juniper gear for the last years, and networking is networking, even though everything Cisco is preferable if you are going for cisco certifactions.
But having the certifications isnt everything. As long as you have documented experience and good references you can do a fair bit without. Personally, I've worked with stuff between CCNA and CCNP level for the last 4-5 years... and even out-troubleshooted CCIE a few times, do I have a cert... no... although I have the books so I will probably end up taking CCNA/CCDA and perhaps something more just because it looks good on the paper. I just find most of the Cisco books quite booring. But I'm moving over to the security side and CISSP come autumn so...