Not true - you can keep checking fares continually before final payment. I have done it for the past year (fares never got lower only ridiculously higher). BUT I just had a major issue. A month after FINAL payment I called and had my flights ticketed so I could look at upgrading and BOOM - I was hit with an additional cost of $2200 for my flights and sent an invoice from HAL via my TA. It was a MISTAKE and it took my TA over 2 hours to get it straightened out and nearly gave me a heart attack. They got it fixed but KEEP AN EYE ON THINGS.