Like other prototype defenses, they will only last for a limited duration after being deployed.
The Sky Shield projects a shield for the area directly around itself. Any Gunboat Weaponry that makes contact with the shield will be absorbed and have no effect on the buildings it covers. However, Artillery and Barrage can damage the shield directly.
If its shield is destroyed by Artillery and Barrage, the Sky Shield automatically destroys itself as a result, much like how a Shield Generator self-destructs after its shield on the Headquarters or Power Core is destroyed directly. Likewise, destroying the Sky Shield using ground forces will destroy the shield it projects.
The Sky Shield generator is able to be directly damaged by ground troops, whether they are under the shield or not.
Be careful when using Smoke Screens against a base with a Sky Shield. The Sky Shield can absorb any Smoke Screens passing through it, so you will need to destroy the Sky Shield first or find another route around it.
You cannot Flare directly onto the Sky Shield or onto any buildings it covers, as the shield will simply render your Flare useless.
The Sky Shield only protects against Gunboat Weaponry whose point of impact is within the shield's range (denoted by a faint circle underneath the circular halo the Sky Shield projects). However, Gunboat Weaponry fired outside its range will work completely normally, so you can still, for example, use Shock Bombs on protected defenses if you place the Shock Bomb outside the shield.
It may be more beneficial to use an army composition strong to the defenses protected by the Sky Shield, since it may take too much Gunboat Energy to destroy the shield and the defenses underneath. For example, if the Sky Shield protects some Boom Cannons, mass infantry may be beneficial.