I’m 46, and I would be happy to buy a kever now – in fact, more than one kever – for starters, one for Chavez, one for Ahmadinejad, one for Haniyeh, one for Nasrkaka, one for Ahmed Tibi, one for Noam Chomsky, and even one for George Tzuris, who can afford his own.
Seriously, it is a segulah for long life to prepare a tzavooh. A good idea would be to specify your desired place of burial and to allot funds for its purchase. A statement like “my neshomo will know no rest if my request is not fulfilled” might be appropriate if you know you have relatives who might not follow your directions.
I would like to be buried next to Sholam Weiss. If we hold that dina demalchusa dina, that guarantees me over seven centuries of life.