My NE-2 Relaxation Oscillator is Too Relaxed ???

I am experimenting with a relaxation oscillator circuit consisting of
a NE-2 bulb wired parallel to a capacitor and this pair is wired in
series with a resistor and connected across a 150 V DC power source (a
bunch of DC wallwarts connected in series).  The resistor is variable
0-1 Meg Ohm, the capacitor is a 1uF electrolytic rated at 160V.  I
don't have any capacitors on hand with a higher working voltage.

The circuit seems to work.  I can get the bulb to blink around 3 times
a second but I am wanting a higher flash rate and I am not getting
it.  Lowering the resistance makes the bulb turn on continuously.  I
don't think that the bulb is fla****ng faster than the eye can
distinguish.  I conneded the circuit to an oscilliscope and when the
bulfb is visually fla****ng I see the RC discharge curve but lowering R
until the bulf truns on continuously pretty much produces a flat line
on the scope.

I was expecting to maybe be able to get around 2-100 hz with a NE-2
relaxation oscillator.  Is this possible or am I expecting too much
from this type of circuit?  And if so, why?

Any help would be greatly appreciated.  Thanks