Today's DSLR cameras come with what the factory calls Rated Actuations on the shutter mechanism. That is the approximate numbers of times the shutter is expect to shoot a frame before needing replacement.
For example, the Canon EOS-80D, EOS-5Ds, EOS-7D Mark II and EOS-1D X Mark II cameras are rated as 100K, 150K, 200K and 400K, respectively. The actuation counts are easy for still photos but when videos are added in, it becomes a little bit trickier to get an accurate measurement.
My readers know me as The Wildlife Ho-tographer. I have been using Canon gear for about three decades and have taken many pro gear on global wildlife photo shoots. You can follow my travels on Facebook and Twitter. See my equipment bag and works on MichaelDanielHo.com
Personally, I find this Shutter Count fascination to be nothing more than an academic curiosity. For professional grade cameras like the EOS-1D Mark IV or EOS-1D X Mark II cameras, their shutters are rated conservatively at 300,000 and 400,000 actuation, respectively.
Many photographers, including myself, have multiple bodies anyway and the chance of any one of the pro bodies racking up 300 to 400K actuations is small because one would have upgraded to a newer model anyway. However, I know a friend who owns the EOS-1D Mark IV and is still using the original shutter after raking up half a million actuations. Besides, getting a new shutter is not that expensive anyway.
When one has been out in the field long enough using pro equipment, one will discover having the dreaded Err 20 appearing on the LCD screen due to a shutter failure is slim to none, if one's gear is properly cared for with recommended factory maintenance. More often than not, there are other problems, like a circuit board failure, etc. It happened to me twice with the EOS-1D Mark IV and EOS-1D X while on wildlife photography shoots overseas.
If you are interested in finding out what your camera's actuation count is, read my earlier post on this subject and download the software to track your usage.