There seems to be some, but not a lot of ipe data already on this
newsgroup. I'm preparing to have a ~500 ft^2 deck replaced using 1x6
ipe (the old deck was 2x6 cedar). Because there is almost no local
experience using ipe I've had to spec out everything myself to decking
contractors. I think I have most of the topics covered (anchorseal, ss
fasteners, carbide teeth on saws). I'd really appreciate if anyone
could provide their suggestions on:

500 Feet squared is 500' X 500', that is one big deck. Do you mean 500
sqft?

1.DRILLING: What is the optimal drill type for drilling & counterboring
for 3/8" plugs? My current ideas a
a. drilling two separate holes: 3/8" carbide forstner bit for the plugs
and 3/16" carbide brad tipped for the screws or
b. HSS drill bit/countersink/counter bore kit from Lee Valley
Any recommendations on material/drill type/ease of sharpening?

I recommend the inexpensive HSS drill-countersink combo type. Buy a bunch
of them and throw them out as they become too dull to use. Drilling the
same hole twice is a huge waste of time, especially when you are talking
about several thousand holes. Buying expensive ones and trying to resharpen
them is also more time and hassle than it's worth.

2. My existing deck is 25 years old. The framing is 2x10 treated @ 16"
centers and upon inspection it looks very sound- no rot/soft spots.
I'm not sure how to evaluate how many years may be left in it. Of
course, I don't want to put a 40 year deck on a frame with 10-15 years
left on it. Does anyone have real experience with life expectancy of
1980 treated lumber vs. today's treated lumber? These joists look a
lot straighter than what I've seen lately at Home Depot. Cost to
reframe is ~$2500 using 2x8's.

Any and all advice from experienced ipe users is welcomed!
Thank you.