I think everyone should cross train, getting perspective on what you do is a hugely valuable thing.
It has it's down side of course, which is why you have to pay attention of how the new things you are doing effect what you already know. It can be a positive effect, or a negative one, as some martial arts are more complimentary to others, whilst others have a whole different methodology and ruling concept that drives them. This is where understanding context comes in, and understanding what concepts cross over and are applicable to both arts, and what are only applicable to one or the other.
Sonny was always very adept at telling if a student, who had perhaps been absent for a couple months and returned, had been training in another art. "Ah, you've been training Wing Chun/Silat/Shaolin I see".
Spend time training an art that emphasizes forward pressure, closing distance, taking angles, or focuses intent on the center line for instance, and you'll get a corresponding reaction with a pinuti in your hand.
Spend time with a different sword design, say a thin, narrow, point weapon, and what you need to do to prevail with that, might come out when using a heavy, short, edged weapon ..... and vice versa .... often not good in my experience. However, to defend AGAINST an unmatched weapon you have to understand this.
All systems of thought, and weapon designs should have a logic behind why you do what you do, with what you have in your hand - they work because A, B, C .... so to defend against, you'll need X, Y, Z
All this stuff comes out in random flow or sparring, and that is why these practices are invaluable for understanding what pieces fit to what context.
Nothing shows up flaws like trying to hit someone whilst they are trying to hit you, using the same system/weapon, or with something completely different.