How to use "attention span"

I found the following first sentence on one of online videos. I know if someone have a short attention span, they cannot focus on a task for a long period of time. However, I'm not sure about the opposite expression. Therefore, I would really appreciate it if someone could let me know whether the second sentence is natural and grammatically correct. The main reason for my question is I when I checked the Ngram results, as you can seen in the bottom of this question, to compare the usage of these two expression, the usage of "long attention span" is far lower than of "short attention span"

I have a bit of a short attention span

I have a bit of a long attention span

Ngram results:-

https://books.google.com/ngrams/graph?content=long+attention+span%2C+short+attention+span&year_start=1800&year_end=2008&corpus=15&smoothing=3&share=&direct_url=t1%3B%2Clong%20attention%20span%3B%2Cc0%3B.t1%3B%2Cshort%20attention%20span%3B%2Cc0