If you launch a first strike, I don’t see why it would matter whether retaliation comes in half an hour or a day.
What would matter is whether that first strike or a later follow-up could take out the shuttle(s) before it could retaliate.
Did the USSR have capability to take out a space shuttle in orbit? I wouldn’t know. It wasn’t that high up (a V-2 could almost reach it), but accuracy of ICBMs wasn’t even good on stationary targets, and, I guess, you would need more of it in space, where ‘only’ radiation and heat would cause damage.
In case of retaliation you want it to be delivered soon, ideally before you and the retaliation infrastructure is destroyed. If the retaliatory strike is already in flight before the first strike can even reach the enemy territory (or sattellites, etc.) then it is much more difficult to prevent.
That's why the response time is so crucial. To ensure retaliatory strike strikes fear in your enemy (pun intended) you need to convince the enemy you are capable and willing to put your ICBMs before their ICBMs can even reach you. If you have only 2 minutes you need to convince the enemy you are willing and capable to do it within 2 minutes of detecting the strike.
You also want retaliatory strike to be delivered all at the same time as the best strategy seems to be in numbers. It is relatively easy to stop a single ICBM. It is completely different problem to stop hundreds of them each possibly containing multiple warheads. In this case the strategy is to deluge the enemy with warheads or, more precisely, hope they will not try to destroy you because they can never be sure to stop all out retaliatory strike.
The primary job of a first strike is to take out as much of the target's retaliation capability as possible. Objects in stable orbits are much easier to track, target and destroy that just-launched missiles (or shuttles) because you can take your time to identify them and line up your anti-satellite systems.
What would matter is whether that first strike or a later follow-up could take out the shuttle(s) before it could retaliate.
Did the USSR have capability to take out a space shuttle in orbit? I wouldn’t know. It wasn’t that high up (a V-2 could almost reach it), but accuracy of ICBMs wasn’t even good on stationary targets, and, I guess, you would need more of it in space, where ‘only’ radiation and heat would cause damage.