Sometimes, the better compromises are those that fall in between. I understand the frustration of having to change lenses in between shots- because it seems like you are at either one end or the other- constantly swapping lenses. However, this is POTN, and you probably should state how much you are looking to spend- like a range or this much maximum, otherwise you will get a lot of suggestions that might be way out of your budget.
When all I had was the combo you have now- I looked at and decided upon another kit lens- the 18-135 - long enough to catch most stuff. Not too long. relatively light. Carried a longer zoom just in case- but the 18-135 is typically enough range.. I found that the 18-55 was versatile for in a room- but outside- it often lacked as a walk around lens. But if you narrow down your choices to what your budget will allow- more applicable choices will surface. Right now, I could only guess whether your budget was $500, $900, or $2600..
EOS 5D III, EOS 7D,EOS Rebel T4i, Canon 70-200 f/2.8 IS II, Canon 24-105L, Canon 18-135 IS STM, 1.4x TC III, 2.0x TC III, Σ 50mm f/1.4, Σ 17-50 OS, Σ 70-200 OS, Σ 50-500 OS, Σ 1.4x TC, Σ 2.0x TC, 580EXII(3), Canon SX-40, Canon S100
Fond memories: Rebel T1i, Canon 18-55 IS, Canon 55-250 IS, 18-135 IS (Given to a good home)...