Hi Matt. The longer macros certainly have some advantages over shorter focal length lenses and, given your particular herp interests, I think these would fit your needs nicely. But I bet you may end up getting a shorter macro too. They are much easier to shoot hand held and have a few other pluses as compared to the big macros. I use my 105 and 180 about equally (the 105 serves as a decent portrait lens too).

As you know, Nikon does not make a 180mm macro, but a 200mm. My 180mm is a Sigma. I snagged it new off ebay for $439. A 200mm micro Nikkor would be much more $$ and only a slightly better performer. I hear the Tamron 180mm is also a sweet lens and comparable in price to the Sigma. I went with the Sigma instead of the Tamron because it seems more solidly built and shooting herps in the field can certainly test lens durability.

Regards,

Wasil