If I read the datasheet of the MKR 1000's MCP73830 battery charge management chip correctly, no. It is a fixed 4 hours.
Power is programmed by the RPROG resistor on the PROG pin of the MCP73830 (R3 on the MKR 1000). You can see the equation in section 5.4 of the datasheet:
IREG = 1000 / RPROG
So you could solder another resistor in parallel to R3 to get a higher IREG