Hi I haven’t read any of the previous so apologies if I repeat the obvious.
I am finishing the ‘minor corrections’ of my thesis, had my viva in december (molecular modelling).
It’s a great experience, it can be hard, depressing, frankly horrible but looking back to it I think it was the best that happened to me (mainly because it got me out of the 100km radius I lived in).
Make sure you really are motivated. You don’t have to end up in the academia. You won’t unlearn what you already know. Just add more skills to your CV.
Be prepared to deal with an awfull lot of stress and be able to work 12 hours a day 7 days a week