  We study the dynamic behavior of frameless ALOHA, both in terms of throughput
and age of information (AoI). In particular, differently from previous studies,
our analysis accounts for the fact that the number of terminals contending the
channel may vary over time, as a function of the duration of the previous
contention period. The stability of the protocol is analyzed via a drift
analysis, which allows us to determine the presence of stable and unstable
equilibrium points. We also provide an exact characterization of the AoI
performance, through which we determine the impact of some key protocol
parameters, such as the maximum length of the contention period, on the average
AoI. Specifically, we show that configurations of parameters that maximize the
throughput may result in a degradation of the AoI performance.
