If your bore, piston and rings are in good shape you will not have to have it honed/re-ring, therefore there wont be so much of a break in process. As far as the reliability goes, more power is slightly harder on your bottom end parts...but, a conservative port job if done correctly won't decrease your top end reliability. In many cases I've seen ported top ends last longer than stock due to more efficient scavenging (more of the combustion heat exits the exhaust and more cool intake charge enters thus lowering the temp) if compression is kept mild, and more accurate port chamfering extends ring life.