I've gotten nearly identical lifespans out of underarmour and 'actual rashguards,' regardless of if the rashie was sold with MMA/Jits or surfing in mind.
currently rocking: 2x unrderarmour short sleeved, a Nogi Long sleeve, and a Reef long sleeve.
Nogi rashie has held up to a year of rolling 3-5 times a week with only a single frayed spot, and some damage to the logo, couldn't say how the UA stuff will hold up long term, but they've taken a few months of rolling (plus use when I play rugby) with no visible wear.