My snippet only expands after a blank space, why?

Say you want a snippet for "-year-old" to expand right next to the number you type so that it looks like this "12-year-old," but it only expands after a space, so that is looks like this "12 -year-old."

Click on the snippet group that snippet is in, you will see the Group Settings appear to the right.
Set "Expand after:" to "Any character."

That group was likely set to "Whitespace" so that the snippet would only expand after a blank space and not directly next to other characters.

Depending on your abbreviations, you may want to create a separate snippet group specifically for these snippets, and leave your other snippets in a group set to "Whitespace."

Technical Note: TextExpander only sees what you are typing, and cannot always notice the effects of particular keystrokes. For instance, in MacVIM, typing "i" while in navigation mode changes the context and meaning of subsequent keystrokes, but TextExpander cannot detect that, so if you type "iddate" your "ddate" snippet will not expand, unless it is in a group set to expand after "Any character".