I got a bike fit around seven years ago. It was a season where I had really increased my mileage - over the course of the year and for individual day rides. The degree of difficulty also increased, with more climbing on my rides. As the year went on, I had been experiencing increasing discomfort in my elbow and my left knee. About 40 miles into my last century of the season, the discomfort - especially in my knee - got to the point where I was close to making the call of shame to get a ride back to the start. I took around 4 Advil and that relieved the discomfort and I was able to complete the ride. But, it did motivate me to get a bike fit. They swapped out the handlebars and did some seat and cleat adjustments. I will say the fit worked wonders for me and I felt much better after that. I may have been able to figure all that out by doing my own research but, for me, it was money well spent (the bike shop keeps the measurements on file and, when I bought a new bike, they set it up using the same measurements).