I've just added these quotes from a septic plumbers to our file, in case your plumber plays dumb or doesn't want to do the hydro blasting:
http://tinyurl.com/Septic-Solutions
This was an excellent discussion between septic plumbers. Especially the part of Septic Installers complaining to the state about lost revenue from guys cleaning sludge from the lateral pipes in the septic field:

txshriner said:
“Ive been cleaning drain fields for several years with extremely good success, actually with too much success! i did this with the knowledge of the local health department and everything was rosy and then one day a few years back the local health department director stopped my employee and had me call him. he had just come from a big pow wow the installers had at the state level. i dont know what the topic of conversation was supposed to be but it turned into a whining session from the installers! apparantly the several hundred systems that i had successfully cleaned and put back to working had these old boys worried about the money they were missing out on. he told me that he was pretty sure i'd be hearing from someone and i did. a little higher up than i expected, the man claimed to be the number 2 man in the state! we argued for over an hour about drain field cleaning. it was of his opinion that this isnt possible but thats like telling the bumble bee that scientist say he cant fly! i have lost count of how many i have made work that even i thought would never work again. you wont make friends with any installers making old systems work but it does pay very well if your successful at it!” http://forums.colepublishing.com/archive/index.php/t-35.html

Pump the tank and Hydro Blast the laterals before doing anything else. Add risers to the tank & D-Box to make these tasks easier in the future.

Another plumber said,
“Our most popular septic services is Hydro Jetting lateral lines. This allows us to clean up years of sludge build up and give your system the ability to operate at its full potential again. This service requires a few small holes to be dug up in your lawn, the rest of the work is done underground, saving your lawn!”
http://www.reddiindustries.com/services-septic-tanks.php

Another Septic Plumber advised flushing out the laterals whenever the tank is pumped out,

If my septic plumber had not LIED to me and tried to sell me an EXPENSIVE new septic field, and then told me NOTHING else could be done, then this forum & my research would not be needed. Finding the TRUTH about Septic is like running through a mine field!

We are on a roll. My nearly 2 year long septic nightmare is coming to an end, I am writing up the request for quote now to upgrade my septic system:
1) Add risers to each of my Distribution Boxes
2) Hydro Blast the laterals
3) Add a "Settling Tank" between my single chamber Septic Tank & the D-Box with a riser
4) Add a Gray Water system for the washing machine & water softener.

Then relax with no more septic problems, YAY!
Grizz