Depends on how you do it. If you do the two-person way with somebody pressing on the brake pedal and you depress it to the floor, it's possible because the seals may be scuffing in parts of the master cylinder bore that it hasn't touched, and if there's surface rust there, it may damage the seals. Put a block under the pedal to prevent going further than normal.
Or, use a vacuum or pressure bleeder that doesn't use the brake pedal at all, and there's no trouble.
Brake fluid will absorb moisture from the air, even through the rubber hoses. It lowers the boiling point, and causes corrosion inside. Flushing brake fluid regularly is a good idea.
One potential problem is if you've never touched the bleeders, they may not open nicely. If you do it yourself, be prepared in the off chance one breaks off. Be careful if you decide to use penetrating oil on them that it doesn't get into the brake fluid. Anything petroleum based ruins brake system seals.