How far do you dig out horizontally?

To stop me going too far I dig as far as a stone pick takes me.

I don't go too far - I try and stick to a system, so I would dig the first gallery with the ceiling as level 16, and go about 25 blocks, then keep adding galleries spaced 3 blocks apart until I have 10 or so in parallel; I'll then go below my starting point and dig a parallel setup in (hopefully) the same xy layout, so that the floor between them is one block high.

When I finished that, I'll go back to the level above and expand the first shaft another whatever blocks, rinse and repeat. I think all this ensures I find virtually everything in that space, and it seems to be quite scalable as long as you can find your way back... Putting torches consistently on one side helps with that.

Nice, I'll try that technique out.

Providing everything's nice n'tidy navigation shouldn't be too hard - maybe just a torch showing where the main staircase shaft is. I can see what I'm mining even when there's no light source around.

Hmm, maybe my brightness is set too high. T_T

Do diamond axes not go through it quick enough?

(only guessing - not had enough resources to make one myself!)

Diamond axes and picks see to do the job in the same time, but not quick enough.

My original issue with wood was having to go treking around for it but then I realised I should just plant my own little forest in my complex that I renew each time I cut it down.