I love this game idea. I really enjoy strategy games. The tower defense genre mostly seems to be focused on planning, with a little bit of action/reaction during a wave. But adding in a mechanic where you have to constantly manage your towers to keep them in peak condition adds an RTS element that is really cool.
It could be interesting if there was more risk to using time as a resource. In this implementation of the game, the time resource technically could have been any resource really. Like if I gained 1 water every second and could use 10 of it to cooldown overheating turrets to keep them warmed up but not melted. That would be the same mechanic with a different aesthetic. Although that would not account for the manual aging of turrets... Just thinking "out loud" about how your use of the limitation is sort of like an abstract version of any resource that is arbitrarily gained over time. Perhaps that is a little food for thought, or not very useful. Not saying your use was bad by any means. Back to the more risk thing. If the player could temporarily sacrifice their grandfather clock's life as extra time dropping their time resource to a negative value. That is then restored if the player lets enough time pass to get back into a positive value. There could be some interesting risk reward dynamic there. Like should I go into time debt so I can deal with the current state of this wave and hope I do not take any permanent damage in the process. Okay, rambling done.
Fun and enjoyable lil' experience. I suppose like life, it was only inevitable that I was going to lose to the ever increasing spawn rate of red blobby dudes. Keep up the good work.