I shoot about 400-500 pictures every day. Many of them are in burst mode. Will this wear out the shutter? I bought a Rebel 1200 D and five months the shutter gave error 30 and had to be repaired. Is it because of too much shooting in burst mode and flash?
It doesn't really matter whether shutter activations are in burst mode or not. What matters is that they happen. 500 shots per day for 150 days is 75,000 shutter activations! Canon no longer provides shutter ratings for the Rebel series but back when they did the oldest Rebels and later lower priced models had ratings of 50,000 activations while the later higher priced Rebels had 100,000 cycle shutter ratings. Your shutter failed almost exactly halfway between 50K and 100K. It sounds like you just wore it out.
It's just like miles on a car: they cause wear and tear whether it takes six years or six decades to put a million miles on one. Most cars won't last a million miles. Most 1200D Rebel shutters probably won't last much more than 75,000 shutter cycles either.
If you bought the camera new I'd be interested to know if the shutter replacement was covered by Canon under warranty.
From what I've read online, Err 30 is almost always a shutter failure, consistent with Canon's documentation for this specific error ("a malfunction with the shutter has been detected"). You should be able to get the camera fixed under warranty; if not, replacing the shutter would cost about $200 to $300—not worth it for a 1200D.
While newer Canon EOS Rebel models have no official shutter rating, similar entry-level Nikon DSLRs like the D3000 series have shutters rated for 100,000+ actuations. More advanced bodies are typically rated for at least 200,000 or 300,000 cycles (my Pentax K-3 II is rated for 200,000 cycles). Bear in mind that this is an MTBF value; the shutter can fail much earlier or later than this.
400-500 shots a day is extremely heavy use for an entry-level DSLR and I'd strongly recommend that you upgrade to a more advanced camera body. These kind of low-end DSLRs are typically only designed with the expectation that the user would only shoot a few dozen to a hundred or so pictures a day. I'd probably recommend the Canon EOS 7D Mark II (rated for 200K cycles) considering your usage profile; sadly, the more affordable 80D is rated to only 100K cycles.