I have decided to refinance my home mortgage. On the current mortgage
I pay $2000 a month. These payments will last for another 96 months.
The new mortgage will require a monthly payment of $1500. These
payments will also last for 96 months. The refinancing cost(closing
points, etc.) is $3500. The new interest rate is 8%. The net present
value of your savings or costs from the refinancing(i.e., the
difference of my incremental costs and savings in present value $s)
is: what?

holla - 

Not knowing what your cost of capital is, I assumed it is equivalent
to the 8% you had quoted as the designated interest rate.

Basically, then, your gain is $500/month discounted at 8% p.a. for 96
months.
What you need to do is calculate the net present value of your gains,
then subtract the cash outlay of $3500 at time 0 which is the cost of
refinancing.

The monthly interest rate is - 0.006667%
The NPV of all those payments is - $35,368.99
The gain is $35,368.99-3500= *** $31,868.99 ***

Sounds almost too good to be true!!
If you'd like me to recalculate this with a different cost of capital,
let me know - will be glad to run the numbers again.  Also, let me
know if you want more detail - I ran this in an Excel spreadsheet,
could somehow copy that to here if necessary.

thanks,
ragingacademic

For fun, here's what it look like to me but check with your CPA if the
result matters to you: If your sales started at 1 and rose 12 % in one
quarter to 1.12 and you want to know what they would be if that trend
continued for 4 quarters, then the answer you want is 1.12 x 1.12 x
1.12 x 1.12 which is the same as 1.12 to the power of 4 which is
1.57351936 or 57%+ per year. Projecting that growth out 20 years you
get 1.57 to the power of 20 which is 8,279 times more than you started
with. The calculation is trivial, the judgment to know it will not
happen may be harder.

Woops. This comment was to another one of your questions.