Won't hurt nuthin for you to measure your SG at higher temp...but it "does" throw the reading off and you have to correct for it. Most hydrometers are calibrated for either 20c or 60F. Some come with a temp correction reading/therm built in. Most of us have to look up the correction in a table. The first hydrometer I had was calibrated 20c and it was "easy". Plenty of correction tables around for that. I finally broke that after a few years, and had to get a new one. New one is longer, thicker and calibrated for 60F. It's harder to find a full correction table for that.
I think Dnder also said, those corrections can vary by manf. Mine didn't come with any kind of table etc., or instructions. But, I think its safe to say...that if you are fermenting at 80F now...that your OG reading was probably closer to 1.060 than 1.055 after correcting for temp. To give you some perspective, my first AG mash was 1.030s. Later on I managed to get it up into the 1.040s. Might have hit a 1.050 somewhere along the way. I usually got back far less volume as well. Out of all the above, It would usually give back about 1/2 gal of low-wines and that was stripping it down to the bone.
You did better than I did my first entire year of mashing on your first shot!