Hi aamex,
Here are my thoughts, hopefully someone smarter than me will chime in as well!
First, you should never pay interest for a score - if you are only getting a mortage to "diversify" your accounts, that's a bad idea. Now if you are actually house shopping and want/need a mortgage, that's fine.
I like your excel idea, sounds cool and more exciting than nothing!
I don't think that small a difference in AAoA will matter - but waiting for a 3 year+ average might be better, if it doesn't take that long....and also, having 30 inq is quite a bit, letting some of those fall off would probably also be better, and help raise your score.
You said you are "gardening" but with what score? If you are over 750, and need a mortgage, waiting won't really matter, but if you are under 720, 680, or other benchmarks, then waiting is important for a better interest rate if you can wait for the mortgage.
I hope that helps - basically, don't get a loan just to "diversify" and even though gardening is boring, it'll be something you do your whole life, so you might be doing it more than "6 months to 2 years"....get used to it now.
Starting Score: 799
I'm also gardening. I've created the excel worksheets that track my util, inquiries (score fall off dates and report fall off dates), and AAoA. My worksheet has my AAoA at 4.6 and 4.5 for EQ and TU. However, both my reports say my AAoA is only 4 years, which correlates to what I've heard about the AAoA being rounded down for scoring purposes. So an AAoA of 2.88 or anything under 3 would still be an AAoA of 2 years. If I've mistated that, please let me know!!!! Then once you get to that AAoA of 3 years and you open a new account, you'll be back down to 2 when the new account hits. So as posted above, if you are just looking to diversify your credit mix, this might not be that beneficial. Look at your goals and go from there.
Are you positive it's diversity which is keeping your scores from changing? What is your utilization..are there any derogs you're unaware of..with a 702 FAKO it's hard to say what's going on without an actual FICO score and credit pull...
It's a FAKO, which is controlled by the season on R8!4183U. You need a degree in Astrophysics and meteorology to predict it.
Starting Score: EQ 583 TU04 619 EX 592 (lender pull) 2010I tried pasting a screen shot of my worksheet but it's not cooperating with me at the moment. 
Basically I listed all of my accounts and their respective balances. I divide the total of my balances by my total available credit to track my total utilization. I also track the individual util per account. I track the change in percentage monthly. It looks kind of like this. (Edited to include actual worksheet shot, finally)
| Date | 3/11/2011 | 4/11/2011 | 5/17/2011 | 6/17/2011 | ||
| Account | Limit | Balance | Balance | Balance | Balance | UTIL |
| Dell | $5,000.00 | $2,899.38 | $2,783.99 | $2,596.90 | $2,191.54 | 43.83% |
| CFNA (t) | $2,200.00 | $1,076.44 | $1,033.44 | $983.44 | $838.44 | 38.11% |
| CFNA (k) | $2,200.00 | $1,022.99 | $922.99 | $863.57 | $563.00 | 25.59% |
| JcP | $1,800.00 | $0.00 | $0.00 | $0.00 | $12.69 | 0.71% |
| Juniper | $3,500.00 | $2,021.71 | $1,615.44 | $0.00 | $0.00 | 0.00% |
| BB | $500.00 | $39.90 | $0.00 | $0.00 | $0.00 | 0.00% |
| MilStar | $6,850.00 | $234.00 | $0.00 | $0.00 | $195.00 | 2.85% |
| Target | $200.00 | $22.36 | $0.00 | $0.00 | $0.00 | 0.00% |
| NavyFed | $15,000.00 | $0.00 | $0.00 | $3,313.00 | $2,599.00 | 17.33% |
| $37,250.00 | $7,316.78 | $6,355.86 | $7,756.91 | $6,399.67 | ||
| Closed Accounts | ||||||
| Tribute | $2,250.00 | $1,743.32 | $1,691.97 | $1,640.38 | $1,488.58 | 66.16% |
| Total CL Available/Used | $39,500.00 | $9,060.10 | $8,047.83 | $9,397.29 | $7,888.25 | |
| Total Utilization | 22.94% | 20.37% | 23.79% | 19.97% | ||
| Change in UTIL | (2.56%) | -3.42% | (3.82%) |