So many of us using High Sierra with a 3rd party SSD have been experiencing slow boot times, sometimes up to a minute. This is in comparison to around 20 seconds on Sierra and below. I had an issue where my machine could not see public or developer betas, so I wiped my machine clean and installed 10.13.3, updated to 10.13.4 dev beta (17E160e) and then enabled TRIM. My machine now boots up in about 30 seconds, which is markedly faster than before. While wiping and starting over from scratch may not be for everyone, it worked for me. YMMV and always backup!