Determining the timescales of magma degassing is essential for understanding the mechanisms controlling the eruption style and the dynamics of magmatic systems. Towards this end, we measured ²¹⁰Pb-²²⁶Ra disequilibria in andesite lavas erupted from Volcán de Colima between 1998 and 2010. (²¹⁰Pb/²²⁶Ra)₀ activity ratios range from 0.86 to 1.09, and are best explained in terms of ²²²Rn degassing and accumulation. The range in ²¹⁰Pb deficits indicates that the timescales of ²²²Rn degassing did not exceed 11 years. ²¹⁰Pb excesses are rare and small (<10%), which signifies that ²²²Rn degassing is more effective than ²¹⁰Pb accumulation in this intermediate system despite the relatively low gas output at the surface. The absence of significant ²¹⁰Pb excesses strongly suggests that the volcanic activity results from episodic ascent of small magma batches through the vapour-saturated section of the magmatic system. Overall, the degassing models based on ²¹⁰Pb-²²⁶Ra disequilibrium suggest an open and complex subvolcanic magmatic system comprising several conduits in which multiple magma batches reside for up to 10 years. Shifts from effusive to explosive Vulcanian eruptive phases are not related to changes in degassing mode on timescales resolvable using ²¹⁰Pb-²²⁶Ra disequilibria.