4-5 years? I hope you live alone! Every 1-3 years is normal for a typical septic load.
I had a 1000 gal tank - I pumped it every year. I recently replaced my system and put in a triple-chambered tank that totals 2250 gallons, and also doubled the size of my existing leach field. I did the system design, but hired out all of the work - total cost was a little over $9,000. The first tank chamber is about 1600 gallons - I pump that every 2 years (about 1/2 of the second tank spills back for a total of about 1800 gallons pumped). When I did it the first time, the first chamber was full of sludge like a normal septic tank, the second was clear water with all of 1/2" of foam floating on the top, and I didn't even bother to open the third chamber. My system will last until long after I am dead.
To the original poster - you probably destroyed your leach field by not pumping your tank, although it is not uncommon for a leach field to fail after 25 years. Once enough solids make it into the leach field, it's all over - a layer forms under the stone and it won't perk anymore.
I saw the work you did making the new field - nice tractorin'. However, it doesn't look like you prepared the bed of the field first. That is supposed to be washed sand and is supposed to be uncompacted (no wheeled vehicles running over it). It's might be OK, but don't be surprised if it fails in a year or two. Also, that type of field system has been prematurely failing in our area after about 5 years. Evidently, the chamber edges sink into the base, which makes the chambers close up and get waterlogged. I was going to go with that type of system myself, but was talked out of it by a friends who is in the business.
If your new field does fail prematurely, I recommend removing all of your existing system and installing an old-fashioned stone and pipe field - make it huge if you want. Put in a second 1000 gal tank in series with your first while your at it - tanks only cost ~$700 and a second tank will easily double the life of the leach field.
JayC