DD has been in speech therapy at school 2.5 years. She graduated from speech today. She has had the same SLP for the last 2 years. Would you get the school SLP a gift at all? FWIW, she was being seen 2x/wk for 20-30 min/session.
I don't feel it is necessary, so this is more of a personality thing. If you like to give gifts and that is how you are, then sure go for it. I am sure they would feel appreciated. If you are not a gift giver, but still want to do something a heartfelt note might be nice.
After my kids left daycare, I didn't feel any pressure to buy individual gifts for public school employees, but I do contribute to teacher appreciate week and classroom gifts which I know the latter wouldn't include SLP.
A small thank you gift with a nice note is always appreciated but never necessary! I've gotten gifts over the years ranging from flowers to a little plaque with a saying thanking me for helping them find their voice to a programmable ornament with the child saying "thank you" but one of my favorites was a deck of cards, because the child loved to play Go Fish with their speech word cards