There is something called Peacetime/No war time. At that time your average IAF jet availability will be less, Naval Ships will be in Maintenance, Tanks will be in maintenance Yard reserves. MIC like Adani, SSS will operate on reduced Manpower and reduced production output. Now GOI wants to go for war,
Now
1. IAF needs to increase the availability, which takes time.
2. IN needs to get all ships online, which takes time.
3. IA Tanks needs to lubricated, which takes time.
4. SSS/Adani needs to increase the production rate, which means Employees needs to work in OT with proper shift planning.
All these will take the time which we called prep time. Even the greatest US Armed forces will take time to start the machine.
Now if we start the war immediately, depends on the scale, What if IA ran out of NATO 5.6x45mm round, they need to ask MIC guys to supply, now without having the time to increase the production rate, they cannot supply sufficient amount which may end up in shortage. Same with simple Artillery shell.
We can go for war once everything is ready. That is the time we are taking.
Now do we go for short term war. Don't know. Does the sign shows it will be throwing punches? Maybe