A golden rule says that site visitors should reach their target within 3 to 4 clicks, so you're miles away from that goal. There can be no general recommendation, as the amount of categories and sub-categories that you will need depends on the overall number of pics that you plan to add to your gallery. Huge sites suffer from the problem that you encounter: the site is so full-packed with information that it's hard for the visitor to actually find what s/he's looking for.
In your case, I suggest dropping the extra year category, as there will only be a limited number of race days, so the categories within "MRA" should be "12 August 2007 PMI", "17 Dec 2007 Bob Day at PMI", "23 July 2007 PMI", "23 Sept 2007 PMI" and "3 Sept 2007 PMI" - this will reduce the number of clicks by one at least.
As you appear to be a pro race photographer I suggest sending your potential customers through a manually created portal page where you list all albums in a sort of sitemap. This sitemap should reside on a page above your gallery structure - ideally on the very start page, together with a news section that provides directly links to the most recent galleries. As you appear to use a CMS (Joomla I supposse) this should be dead easy.
You might even consider buying a separate domain for the racing stuff, where you can send the race event visitors to. The new domain could just be a redirector that points to
http://performanceimagery.com/imagedb/ (not very search engine friendly btw, nor does that folder name attract human visitors).
Your site loads dead slow for me - I suggest looking into this in detail. If it happens frequently, talk to your webhost.
However, yours is not a technical question that closely relates to coppermine, but a generic "how can I improve my navigation" issue. There are many discussions on this subject lead elsewhere on the internet. In fact, this topic is something that even Jakob Nielsen (the usability guru) doesn't appear to be sure about.