For example, you can increase soap.wsdl_cache_ttl from 24 hours to 1 month by changing its value from 86400 to 2592000.
Please refer to path below, to edit the cache time :
-> Open php.ini and look for below entries :
; Enables or disables WSDL caching feature.
; Sets the directory name where SOAP extension will put cache files.
; (time to live) Sets the number of second while cached file will be used
; instead of original one.
soap.wsdl_cache_ttl=86400 (This represents the cache time and can be tried to increase, please put in time in seconds)