Well, I know this is subjective, but I usually have two walls on any of my teams at one time. But is this a wrong move? Should I be ditching a wall to focus on offensive Pokemon, as far as competitive play goes? Just wanted to see what the answers for this would be.
As many as you like. There is no best team layout or magic team composition. A team can consist of 6 walls or have none at all. It is however important to adapt your playstyle accordingly to your team. It is also vital to design your team based on what you are good at and what your preferred playstyle is. Generally though, prediction is key. If you are good at predicting your opponents attacks you can afford to be more less defensive. Furthermore, the Pokemon you are using themselves are also important. Having two wallso such as Blissey and Skarmory can easily suffice for any team on the defensive/supportive side, since they counter such a vast array of Pokemon. As they can take a hit from nearly the entire OU tier you can invest the other Pokemon to hit back or do something else. Of course, you can use these two with four other walls as well, it's all up to personal preference. If you are playing the lower tiers where the walls aren't so general you might have to use more than 2 to cover the entire tier. For example, Onix and Spritze are great walls in the LC tier, but they quite vulnerable on their own. A Pokemon like Timburr are required if you are to achive the se defensive coverage as Blissey/Skarmory in the OU tier. But the better the Pokemon are the less of their role you have to use on a team. Despite all I said up there, it is all personal preference. No team is better or worse because it have/lacks a certain role. It's all dependant on what the teams creator desire out of it and his/hers matches.
Two walls can help a lot,And in competitive battles,I find 2 or 3 can really catch up if behind etc.2 walls are good,But if you want to you can add more,or take a fast Pokémo to take it's place.Hope I helped :-)