Not everyone thinks the same on the matter of whether or not sending music into a professional mastering studio is a necessity. If the mix doesn’t need any modifying, this means that it is at a perfect volume level, the fades are well done, the EQ is consistent throughout, the compression is right on, and so on. In that case there’s no need for mastering. If these basics are not covered, audiobyray mastering can help you out.
The shorter the release time for compression, the louder a signal will be. The reason is that it takes less time for amplitude to return to normal after being compressed. Short release times cause distortion but the effect can have a beneficial result.
The distortion will amplify the signal, causing it to sound even louder, but this may not be ideal. A good mid-ground for your release time is 50ms if you do not want any distortion.
The general consensus is to use a short release time for all compression, but each compressor has its own quirks and you should experiment with the right settings.