New Work Computer Setup Advice Needed

I need a new computer for work. I recently became a solo attorney and I'm trying to create my ultimate work computer solution.

Location:
By time of use, the computer will be primarily used at the office but I do work from home or out of office frequently.

Useage:
Heavy word processing and handling a ton of PDFs (tens of thousands, some up to many thousand pages long). Heavy web browsing and emailing. Relatively light graphics or video work (creating keynote presentations with videos).

Options:
I want a robust and reliable setup. I plan on holding out for a month to see what's announced but that's all I can wait.

All options are on the table but I'm primarily thinking Macbook+TBD. Now keep in mind that this computer will be my only computer at work. I could get an iMac and supplement the lost portability with my I 2009 MBP (showing its age) for some of this but drop boxing and syncing files seems like a hassle.


Are there concerns from using a macbook in clamshell mode 10 hour a day?

Is a macbook inappropriate to use in clamshell this amount of time for a few years? Are iMacs more robust?

Is like some insight into people who manage their work lives with a macbook only.

Anything I'm overlooking? Any suggestions? I really appreciate the feedback.

 

OSX. I will use VM ware for when I need Windows 7. Budget is somewhat flexible--maybe around $3,500.

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I will be waiting until the next announcements. Maybe a Haswell Retina MacBook Pro and a (hopefully new) Thunderbolt Display will do the trick.
Any chance that a MBA would be enough computer?

 

Thanks for the replies.

I will absolutely be investing in a backup solution. Still weighing options on that.

Follow up question on MBA v. MBP---does the MBA present any greater durability or heat concerns?