It would be great to be able to preview subs in Inqscribe. Currently my subtitle editing tool is Aegisub, which is so awful I try to do as much work as I can in Inq first.

Thanks for your feedback Diego. I've created a separate suggestion for "Display subtitle character count," which you can vote for below:
http://support.inqscribe.com/forums/4206-general-feedback-for-inqscribe/suggestions/7201068-display-subtitle-character-count

In the meantime, there are 2 workarounds to consider:
1. Re-size the width of the InqScribe window to fit the maximum amount of characters per line. If the text spills over into the next line, you'll know it's too long.
2. Copy and paste your InqScribe transcript into Word. You'll then be able to use Word's ability to count characters.

I realize these are not ideal solutions, which is why we're planning a more elegant Preview Subtitle mode.

I was about to purchase the product but I got a request from a Client where he wants a specific maximum number of characters per line and a maximum number of characters per second. InqScribe's limitation for not being able to do this and the unability of previewing the subtitles you make stopped me from purchasing the product.

We'll consider user-defined and/or automatic subtitle duration as part of our planned overall improvements to the subtitling features.

As you note, for now the easiest way to achieve this is to manually insert a time code at your desired out-point. Or, simply copy the "in" subtitle, and add two seconds. Thanks for your suggestion on how to streamline this.