Web.config: forms timeout vs. sessionState timeout

I want to keep users logged in for over a month. So I have my Forms tag:
<forms loginUrl="login.aspx" enableCrossAppRedirects="false" protection="All" timeout="600000" name=".auth" slidingExpiration="true" cookieless="UseCookies" />
Does the sessionState tag effect the ability of someone to stay logged in for a month?  Are there drawbacks with server memory when setting sessionState timeout more than a day or so?
<sessionState cookieless="UseCookies" mode="StateServer" stateConnectionString="tcpip=loopback:xxx" stateNetworkTimeout="1440" timeout="1440" />
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