Yes, but there's also a point in time where you've got your foundational techniques to an A level and most of your intermediate techniques to a B level and you're starting to plateau on those. It's not a bad time to add in some advanced techniques to shake things up, so long as you still spend time keeping your foundations and improving your intermediate ones.
I am a 3rd degree in TKD and an orange belt in Hapkido. While I think that eventually the Hapkido will be very useful to have, and will maybe take over Taekwondo as my preferred set of techniques to use in a real situation, if I needed to defend myself right now I'd use Taekwondo, because I'm much more comfortable with that.
But if you're at a point where you still have a lot to work on to improve the techniques you do know...well, then do that.
i think if Hapkido had groundfighting, in lieu, of so much weapons it might be close to perfect, at least from a technique driven MA view.
i have yet to train hapkido, but have had a fair amount of exposure to aikido. While they are not the same.... If i could have had it differently, it would have been Hapkido, not aikido that i was exposed to.
I am grateful for the experience that i had in aikido, i truly believe that hapkido is more practical, than aikido.
The reason for this belief, is the philosophical underpinnings shape the training. Aikido's overall approach to the issue of violence, and Hapkido's approach are night and day different.
While there is a lot of convergence with regard to biomechanics and trapping/locking.... one is (in my personal opinion) too receptive and too passive... which isnt budo, while the other is far quicker to go to war and escalate (with agreessive striking and kicking) until a decision is obtained.
i did improve a huge amount with my kote gaeshi,
and Aikido's nikyo is frankly superb.
I wish there was a university that had a number of colleges on campus that were just MA disciplines.
I would take wing chun, hapkido, uechi ryu karate, judo and bjj. as my core group studies. and as minor electives... FMA of some kind, and muy boran.