Hi Suyog,
1 hour sandbox time limit is normal for that module and should provide enough time to complete the exercises as directed. If your sandbox expires you may activate a new one.
The amount of time before sandbox expires will vary depending on the module. Durations between 1 to 4 hours are common.
Are you having trouble completing the exercises in the time allotted? Or are you wanting more time to practice the same exercises repeatedly? Something else?
Please click Accept Answer and upvote if the above was helpful.
Thanks.
-TP