Schengen visa requirements and "validation"

Formally, you don't need either a reserved ticket or confirmed hotel reservations. What's absolutely required according to the relevant EU regulations is merely the financial means to cover the costs of your stay and buy a ticket back to your country of residence. That said, the consulate will also want to know the purpose of your trip, so everything you can provide to support that is useful. Itinerary, tickets or hotel bookings are examples of such “supporting documentation” but not explicitly required as such.

As a first-time applicant, you are unlikely to get a visa without this documentation and you would typically be issued a visa covering the period of your trip (plus a short buffer at the end) so your question would be moot. If you have been to the Schengen area before and can show that you need it, you can get a multiple-entry visa valid for a year or more. You can then use such a visa whenever you like, within its period of validity, providing you respect all the other conditions (having health insurance, sufficient financial means, not staying more than 90 days in any 180-day period, etc.) In that case, waiting before the first trip is not a problem.

If you do show up at the border somewhere unexpected, you might expect to be asked about that by the border guards and if you don't have a convincing reason for being where you are they can cancel your visa or at least deny entry. For example, the Handbook for the processing of visa applications and the modification of issued visas describes the following situation as one in which the visa should be annulled (p. 101):

A Russian national holding a single entry visa issued by the Italian consulate in Moscow arrives at Brussels airport (Belgium) and has no proof of a connecting flight from Brussels to an Italian airport.

So the visa does not automatically expire but you can still run into problems if you don't use it as intended. This is especially relevant for single entry and two entries visas, as they are implicitly tied to a specific trip. It's perfectly fine to use a multiple entry visa for different purposes (say regular professional trips to one country and occasional vacations in other countries).

It really depends where are you going to apply the visa as well. If you're applying your visa in your home country in this case (India) then you might not need confirmed or reserved tickets. However, I think it's quite general if you're applying the visa from any other country that you might be a permanent resident of that country. You might need some kind of booking confirmation or some kind of proof that you have a stable job. I have to show confirmed tickets every time I apply for Schengen visa. I'm Thai national and living in the UK. It's best to check with the embassy which you're going to apply.

Regarding any unused visa, I have been in that situation before and I didn't have any problem or questioned when I applied for my next Schengen visa. Also, it varies case by case. Hope this helps.