and a lot of people skip the conversion test for these reasons:
1. today's modified malts have great diastatic power, and many times fully convert in 30-45 minutes, so 60 mins guarantees conversion
2. any tiny particles of grain are likely to turn black during the test, giving you the false reading that conversion hasn't completed yet
people here, or your LHBS should be able to clue you in to which base malts aren't well modified and might be quirky about converting.