Previously, Google Posts had a 100 to 300 word limit in your Google Posts. Now Google has a 1,500 character limit for Google Posts. It is a more precise number and lets those writing Google Posts know exactly when Google will cut them off.
You can see from a screen shot back in June there was the 100-300 word limit and now, Google shows a 1,500 character limit:
So is this longer and gives you more space than before? Well, it depends on how many characters you use on average for a single word. But generally, one would think 1,500 characters is longer than 300 words.
Forum discussion at Local Search Forums and Twitter.