I replaced the resistor with one of the lamps and the result is pretty interesting, even though less reliable than with 10 Ohms.

The frequency is lower, like 3Hz instead of 13Hz. The lamp slows the charge down as it warms up, but the resistance increases with the temperature. It's a fragile balance and often the system gets stuck in micro-oscillations, due to bouncing.

Using the thermal delay is attractive because it is both "visually explicit" and takes less room. I'll be thinking about it while sleeping ;-)