It wasn't that much work, but yesterday I was too tired to do math when I had some free time, and today I had company over.
As a limiting case, if you start the game by finding 5 items with a Wisdom bonus, you would have to earn enough experience to reach level 31 before the bonus would give you a full level, and 62 before it would result in 2 bonus levels.
With your values, by the time you earn enough experience to reach just over level 33, the Wisdom bonus will have given you an extra level. You would not be able to get a full 2 level bonus until you had earned enough experience points to reach just over level 62.5.
How long you continue to wear the items with a Wisdom bonus is up to you. At least after you hit level 34 the bonus is less significant, though it will help you level a little faster.
EDIT: Lets' say at level 25 you decide to replace one or both of the pieces of equipment with a Wisdom bonus. Dropping down to level 4 Wisdom would increase the amount of experience you would have to learn to just over level 38, while level 3 Wisdom would make it character level 48.6. You wouldn't be delayed terribly much by removing one of the pieces of equipment (an extra 5 levels), but both would put achieving the bonus level fairly late in the game.
Calc, the spreadsheet program in
OpenOffice, contains an equation solving function which is good enough for this application. I did a couple test cases on my calculator, and then did up a spreadsheet in Calc, which anyone can use to check various scenarios. Since the experience required to reach a given level is proportional to the cube of the level, though, you are probably not going to get significantly different results than the cases discussed above.
Wisdom spreadsheet (11KB) - ods file, OpenOffice Calc v2.0.3
Note: There are columns in the spreadsheet for experience, which will not match the numerical values in the original post. I dropped the (1000/3) term, since it cancels out anyway, so you would have to divide the displayed value by 3 to get a result in thousands of experience points.
EDIT: I have updated the spreadsheet to be able to handle the removal of equipment with a Wisdom bonus, though have not done extensive testing. This can allow you to determine what effect changing equipment might have on the Wisdom bonus.
