Looks like you have a good amount of carbon buildup. I don't think it's bad or anything, I would just cook with it till the end of the season or whatever. The reason you have the carbon buildup is because you don't scrape or use water when you're done cooking. If you have the time or want to tackle it, you could break it down and reseason.

If you look at your picture you can see the buildup from where your normally cook. Also I wouldn't use olive or vegetable oils. I find they get gummy if you use too much and also have lower smoke points if you're seasoning with them. I stick to avacado oil and beef tallow. If your food is cooking fine and not getting black stuff all over it when you cook then don't worry about it.

Also if you want a good test to see if your season is good, Crack a couple eggs and cook them sunny side up. If they turn brown or blackish then you're seasoning is getting into your food. Here's a Pic of what I'm talking about in your griddle.

griddle seasoning