1) First. The Crucial M4, Samsung 830 have an excellent track record on reliability (M4 has been out a little longer on than the 830. Could and the pletor M3/5, but have no personal experience. While the 840 pro Has not reallybeen out long enough, based on Samsungs 830 track record it would be an excellent choice.
2) Unless your igo needs satisfing by looking at benchmarks - You will see very little diff in real life day-2-day performance. And that is comparing my M4's (have 3), my 830's (also have 3) and my newest addition the 840 Pro. Benchmark are something else. The Overall score from as ssd for M4 and 830 run around 700 give or take 50 while the 840 Pro is on the order of 1100->1200. Big diff in benchmark, little diff in real life.
3) In general, I have some 14 SSDs dating back to the Intel G1 and G2 and have yet to see a failure.
Added, I DO recommend you follow the more recent recommendation of leaving 20->25% of the drive free vs the old 10->15%.