Firstly, need to remember ENB in particular has a strong US presence, more so than TRP but still.. both have significant operations in the USA. I don't see oil demand rolling over (shrinking) for another 10+ years, and I suspect NG demand will keep increasing as coal fired generation is phased out and NG peaking plants will be necessary to stabilize the grid from notoriously cyclic renewable wind and solar farms.
IF that is the case, the new growth will be in NG shipping capacity additions, and oil will hold its own...for the most part. That will limit growth of the asset base and revenue increases so I wouldn't pay growth multiples on either stock for long. At the same time, as long as both of these companies invest smartly with 20-25 year shipping contracts to mitigate the risk of stranded assets, and only invest where the opportunities are likely to be sustained, these stocks will be cash generators for a very long time. I see at least a 20+ year runway which exceeds my remaining time in a vertical position.