My battery cycle count surpassed 1000 (MacBook Pro Retina Late 2012)
Lithium batteries lose capacity over time, as you recharge them. Your MacBook can sustain 1000 recharge cycles and still retain 80% of its original capacity (more or less).

What this means is that if your battery originally held 10000 mAh, then in its current state of wear and tear it now holds 8000 mAh (80% of original). When you charge it up to 100%, you're now only charging it to 8000 mAh. Your battery has shrunk by 20%, so to speak.

What this means is your battery drains a little faster than before. But unless the lowered capacity truly bothers you, you've still got some time to go before you need to replace it. If you were okay with it at 81% of original capacity, I doubt you’ll notice a difference at 79% or 75% of original capacity.

Replace your battery when your laptop can no longer operate long enough to accommodate your needs without having to plug in, or when System Information advises you to replace it. If you always use your MacBook while plugged in, you likely won't need to replace its battery before you want to buy a new laptop entirely.

1000 cycles isn't a "limit," only a reference. You can go through many more cycles than that.