If a base is fairly spread out, one strategy is to split the base in two. Use titan/orbital/deathstorm to remove long-range turrets in the middle of the base, dividing the base into a front half and a back half. Then you can attack the front half without worrying about the turrets in the back half. Once you've cleared out the front half, move on to the back half. This allows you to gather energy from the front half to use on the back half. Alternatively, if you have a teleporting hero you can just teleport past the front half.
Example: After destroying the beamer near the middle of the base, the turrets at the back cannot attack you while destroying the turrets in the front, and vice-versa. A teleporting hero can easily bypass the frontward turrets, which form the majority of the defenses.