At times you may be advised by mortgage brokers or other financial professionals that you have too many open lines of credit and they are lowering your credit score. I recommend you first check if this is true.
If you feel you do have too many open lines of credit, make your best efforts to preserve your oldest lines of credit. The age of credit lines (kept in good standing) are a very important factor in calculating your credit score. That's why rolling over the balance from one credit card to a new one (in exchange for zero percent interest) lowers your credit score. You replace a high scoring credit line with a lower scoring new one.