Canadian permanent resident applying for USA B1 Visa.

[unvrs]

Hello,

I have a B1 visa related question and was wondering if I can get some advice!

I moved to Toronto from Boston, US in Apr 2006 as a permanent resident. I was in Boston for 6 yrs. on H1-B Visa for an ABC company.
After moving to Toronto, I am telecommunting for ABC, same company I was working in Boston as a full time employee. In Toronto, I am working as a self-employed contractor now for ABC.

In the future, I will need to be in Boston for project related task regurarly for few days every alternate months.

My question is:-

1.) What's the validatidy period of B1-Visa?

2.) Every time I visit Boston, US, do I need to file for B1 - Visa?

3.) USA consulate site [ http://www.amcits.com/usa_visa.asp#business ], gives all the information about the documents. Is it simple to apply for the visa on my own or having a law firm represent me would be advantageous?

Any other advice would be apprecited.

Thanks in advance!

:)