Do you insist on having it able to net you multiple turns? Adding a self-sacrificial cost would enable lowering it's other costs, for example:
Time Distortion

Enchantment
Whenever an opponent successfully casts a spell, you may put a time counter on Time Distortion.
Remove 4 time counters from Time Distortion; Sacrifice Time Distortion: Take an extra turn after this one.
"When time is of essence, make it into a substance.''Of course, this reminds me of Mystic Remora. If this was made the same way, it would look something like this:
Chronos Vapor
Enchantment
Cumulative upkeep

Whenever an opponent plays a spell, you may put a time counter on Chronos Vapor unless he or she pays

.
Remove three time counters from Chronos Vapor: Take another turn after this one.
"It's not about how long you can hold your breath but how long it can hold you."