Are these #'s OK?

I've been using the BBB method since Aug. of last year(new pool-6/2006). My pool has been so easy to maintain and my water is always crystal clear. So heres my deal, my ph always wants to sit at 7.8. I'll add acid, wait, re-test it will be 7.4. The next evening it will be back @ 7.8. All my other #'s are fine so I figured its ok, right?
I expected to use more acid in the winter and more bleach in the summer, but we have had summer weather now for several weeks and I'm still adding acid every other night or so to keep the ph from rising above 7.8. My alc. has been stable @ 110 or so for several months. Now it seems to be dropping very slowly. We cleaned the filters (carthridge) on Sunday and thats when my alc went from 110 to 100, now its 90.
So I guess I have 2 ?'s.
Is it OK to let ph stay at 7.8?
Should I adjust my alc. now, or just wait and not let it drop below 80?
Here are my current #'s
FCL 6
TCL 6
PH 7.8
ALC 90
CAL 230
CYA 40

Ph is OK at 7.8. But, if it goes to 8 or higher, you'll want to lower it. Leave your alk alone for a few days and see what it does. If it drops below 80, add some baking soda.

Thanks Watermom, I thought it was OK at 7.8 I just wanted to make sure. It just likes to hold there, I don't have trouble keeping it from rising above that but it just does not want to stay at a lower ph. My alk. just started moving so I'll keep an eye on it.
Thanks again,
Anna