Seriously, this IRS logging requirement for this tax treatment is onerous and a pain.They have over-granulized this activity. 

After rectifying why they were originally there, I started treating with an outside pest granules that worked great, problem is a year or so later the main ingredient that made them work so well was outlawed ( diazinon ) after that, every spring I started the battle all over again when the warm weather would come the huge black critters would appear.

just look for that ingredient on the label and you will be good to go.also, for areas such as mulch beds a granulated herbicide like Preen works great.

Shingles are composed of ceramic granules which reflect the suns ultraviolet rays.

I prefer the ant granules sprinkled all around the home, particularly in locations ants are most likely to get in like doorways or window wells.

Dispose of material off site.Supply and install mechanical fasteneres 24" o.c. at roof edge perimiter, cover with 13" wide membrane torch applied.Supply and install Sopralene Flam Stick base sheet membrane to seal roof edges, come with Elastocol Stick primer.Supply and install slope insulation cricket, 1:1 ratio, between roof drains, mechanically fastened.Supply and install Soprafix Base 630 base sheet membrane to seal slope insulation cricket, mechanically fastenedSupply and install standard colour 0.026" (24g) gravel stop metal flashing, come with 6" reinforcement membraneSupply and install granules Sopralene Flam 250 GR cap sheet membrane, torch applied.Thanks!

Granules are still there, no wind damage or anything of that nature.If you were me, based on information I have given you, would you project a re-shingle into the project or would you push it down the road a bit?

I have received bids on just repairing the low slope area where the leak is, and bids on the whole roof.Some of the contractors said the granule content on my shingles was still pretty good and I should get at least 5 more good years out of it.Question is do I pay ~$850-1000 for the repair, then replace the whole thing in 5-8 years for ~$5,000-6,000?

Comes in granules that you load in a spreader. 

Water/bleach solution works well but is more labor intensive, pressure washing is faster but you have to be careful that you don't do it too often as it will knock the granules off the shingle, reducing the life of it.