  Response functions $\langle A_x(t) B_y(0)\rangle$ for one-dimensional
strongly correlated quantum many-body systems can be computed with matrix
product state (MPS) techniques. Especially, when one is interested in spectral
functions or dynamic structure factors of translation-invariant systems, the
response for some range $|x-y|<\ell$ is needed. We demonstrate how the number
of required time-evolution runs can be reduced substantially: (a) If
finite-system simulations are employed, the number of time-evolution runs can
be reduced from $\ell$ to $2\sqrt{\ell}$. (b) To go beyond, one can employ
infinite MPS (iMPS) such that two evolution runs suffice. To this purpose, iMPS
that are heterogeneous only around the causal cone of the perturbation are
evolved in time, i.e., the simulation is done with infinite boundary
conditions. Computing overlaps of these states, spatially shifted relative to
each other, yields the response functions for all distances $|x-y|$. As a
specific application, we compute the dynamic structure factor for ground states
of bilinear-biquadratic spin-1 chains with very high resolution and explain the
underlying low-energy physics. To determine the initial uniform iMPS for such
simulations, infinite-system density-matrix renormalization group (iDMRG) can
be employed. We discuss that, depending on the system and chosen bond
dimension, iDMRG with a cell size $n_c$ may converge to a non-trivial limit
cycle of length $m$. This then corresponds to an iMPS with an enlarged unit
cell of size $m n_c$.
