TPE-HKG is generally ontime and reliably so, however 451 serves NRT-TPE-HKG and NRT sometimes has very bad delays due to their runway limitations. This happens a few days a month (maybe 10% of the time). The F service TPE-HKG is very nice but it is a short flight (analogous to SFO-LAX); personally I wouldn't risk being stranded overnight if that connection is the last flight to BKK that night. Of course CX would pay for your hotel room if you did get stranded (don't get too excited, the airport hotel is nothing special, just expensive).